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console: add console.count() and console.clear()
Both are simple utility functions defined by the WHATWG console spec (https://console.spec.whatwg.org/). PR-URL: #12678 Ref: #12675 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Daijiro Wachi <[email protected]> Reviewed-By: Timothy Gu <[email protected]> Reviewed-By: Tobias Nießen <[email protected]>
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‎doc/api/console.md‎

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@@ -155,6 +155,76 @@ console.assert(false, 'this message will print, but no error thrown');
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console.log('this will also print');
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```
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### console.clear()
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<!-- YAML
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added: REPLACEME
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-->
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When `stdout` is a TTY, calling `console.clear()` will attempt to clear the
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TTY. When `stdout` is not a TTY, this method does nothing.
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*Note*: The specific operation of `console.clear()` can vary across operating
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systems and terminal types. For most Linux operating systems, `console.clear()`
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operates similarly to the `clear` shell command. On Windows, `console.clear()`
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will clear only the output in the current terminal viewport for the Node.js
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binary.
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### console.count([label])
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<!-- YAML
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added: REPLACEME
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-->
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* `label` {string} The display label for the counter. Defaults to `'default'`.
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Maintains an internal counter specific to `label` and outputs to `stdout` the
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number of times `console.count()` has been called with the given `label`.
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<!-- eslint-skip -->
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```js
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> console.count()
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default: 1
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undefined
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> console.count('default')
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default: 2
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undefined
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> console.count('abc')
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abc: 1
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undefined
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> console.count('xyz')
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xyz: 1
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undefined
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> console.count('abc')
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abc: 2
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undefined
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> console.count()
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default: 3
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undefined
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>
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```
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### console.countReset([label = 'default'])
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<!-- YAML
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added: REPLACEME
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-->
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* `label` {string} The display label for the counter. Defaults to `'default'`.
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Resets the internal counter specific to `label`.
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<!-- eslint-skip -->
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```js
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> console.count('abc');
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abc: 1
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undefined
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> console.countReset('abc');
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undefined
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> console.count('abc');
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abc: 1
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undefined
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>
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```
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<!-- eslint-enable -->
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### console.dir(obj[, options])
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<!-- YAML
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added: v0.1.101

‎lib/console.js‎

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'use strict';
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const util = require('util');
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const kCounts = Symbol('counts');
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function Console(stdout, stderr) {
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if (!(this instanceof Console)) {
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prop.value = new Map();
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Object.defineProperty(this, '_times', prop);
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this[kCounts] = new Map();
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// bind the prototype functions to this Console instance
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var keys = Object.keys(Console.prototype);
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for (var v = 0; v < keys.length; v++) {
@@ -96,6 +99,42 @@ Console.prototype.assert = function(expression, ...args) {
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}
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};
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// Defined by: https://console.spec.whatwg.org/#clear
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Console.prototype.clear = function clear() {
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// It only makes sense to clear if _stdout is a TTY.
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// Otherwise, do nothing.
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if (this._stdout.isTTY) {
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// The require is here intentionally to avoid readline being
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// required too early when console is first loaded.
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const { cursorTo, clearScreenDown } = require('readline');
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cursorTo(this._stdout, 0, 0);
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clearScreenDown(this._stdout);
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}
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};
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// Defined by: https://console.spec.whatwg.org/#count
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Console.prototype.count = function count(label = 'default') {
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// Ensures that label is a string, and only things that can be
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// coerced to strings. e.g. Symbol is not allowed
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label = `${label}`;
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const counts = this[kCounts];
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let count = counts.get(label);
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if (count === undefined)
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count = 1;
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else
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count++;
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counts.set(label, count);
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this.log(`${label}: ${count}`);
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};
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// Not yet defined by the https://console.spec.whatwg.org, but
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// proposed to be added and currently implemented by Edge. Having
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// the ability to reset counters is important to help prevent
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// the counter from being a memory leak.
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Console.prototype.countReset = function countReset(label = 'default') {
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const counts = this[kCounts];
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counts.delete(`${label}`);
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};
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module.exports = new Console(process.stdout, process.stderr);
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module.exports.Console = Console;

‎test/parallel/test-console-clear.js‎

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'use strict';
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require('../common');
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const assert = require('assert');
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const stdoutWrite = process.stdout.write;
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// The sequence for moving the cursor to 0,0 and clearing screen down
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const check = '\u001b[1;1H\u001b[0J';
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function doTest(isTTY, check) {
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let buf = '';
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process.stdout.isTTY = isTTY;
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process.stdout.write = (string) => buf += string;
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console.clear();
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process.stdout.write = stdoutWrite;
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assert.strictEqual(buf, check);
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}
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// Fake TTY
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doTest(true, check);
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doTest(false, '');

‎test/parallel/test-console-count.js‎

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'use strict';
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require('../common');
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const assert = require('assert');
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const stdoutWrite = process.stdout.write;
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let buf = '';
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process.stdout.write = (string) => buf = string;
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console.count();
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assert.strictEqual(buf, 'default: 1\n');
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// 'default' and undefined are equivalent
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console.count('default');
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assert.strictEqual(buf, 'default: 2\n');
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console.count('a');
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assert.strictEqual(buf, 'a: 1\n');
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console.count('b');
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assert.strictEqual(buf, 'b: 1\n');
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console.count('a');
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assert.strictEqual(buf, 'a: 2\n');
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console.count();
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assert.strictEqual(buf, 'default: 3\n');
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console.count({});
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assert.strictEqual(buf, '[object Object]: 1\n');
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console.count(1);
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assert.strictEqual(buf, '1: 1\n');
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console.count(null);
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assert.strictEqual(buf, 'null: 1\n');
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console.count('null');
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assert.strictEqual(buf, 'null: 2\n');
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console.countReset();
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console.count();
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assert.strictEqual(buf, 'default: 1\n');
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console.countReset('a');
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console.count('a');
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assert.strictEqual(buf, 'a: 1\n');
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// countReset('a') only reset the a counter
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console.count();
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assert.strictEqual(buf, 'default: 2\n');
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process.stdout.write = stdoutWrite;
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// Symbol labels do not work
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assert.throws(
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() => console.count(Symbol('test')),
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/^TypeError: Cannot convert a Symbol value to a string$/);
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assert.throws(
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() => console.countReset(Symbol('test')),
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/^TypeError: Cannot convert a Symbol value to a string$/);

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