parse.js
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"use strict";
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const fastDecode = require("fast-decode-uri-component");
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const plusRegex = /\+/g;
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const Empty = function () {};
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Empty.prototype = Object.create(null);
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/**
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* @callback parse
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* @param {string} input
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*/
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function parse(input) {
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// Optimization: Use new Empty() instead of Object.create(null) for performance
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// v8 has a better optimization for initializing functions compared to Object
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const result = new Empty();
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if (typeof input !== "string") {
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return result;
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const inputLength = input.length;
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let key = "";
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let value = "";
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let startingIndex = -1;
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let equalityIndex = -1;
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let shouldDecodeKey = false;
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let shouldDecodeValue = false;
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let keyHasPlus = false;
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let valueHasPlus = false;
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let hasBothKeyValuePair = false;
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let c = 0;
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// Have a boundary of input.length + 1 to access last pair inside the loop.
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for (let i = 0; i < inputLength + 1; i++) {
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c = i !== inputLength ? input.charCodeAt(i) : 38;
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// Handle '&' and end of line to pass the current values to result
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if (c === 38) {
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hasBothKeyValuePair = equalityIndex > startingIndex;
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// Optimization: Reuse equality index to store the end of key
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if (!hasBothKeyValuePair) {
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equalityIndex = i;
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}
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key = input.slice(startingIndex + 1, equalityIndex);
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// Add key/value pair only if the range size is greater than 1; a.k.a. contains at least "="
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if (hasBothKeyValuePair || key.length > 0) {
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// Optimization: Replace '+' with space
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if (keyHasPlus) {
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key = key.replace(plusRegex, " ");
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// Optimization: Do not decode if it's not necessary.
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if (shouldDecodeKey) {
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key = fastDecode(key) || key;
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if (hasBothKeyValuePair) {
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value = input.slice(equalityIndex + 1, i);
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if (valueHasPlus) {
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value = value.replace(plusRegex, " ");
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}
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if (shouldDecodeValue) {
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value = fastDecode(value) || value;
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}
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const currentValue = result[key];
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if (currentValue === undefined) {
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result[key] = value;
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} else {
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// Optimization: value.pop is faster than Array.isArray(value)
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if (currentValue.pop) {
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currentValue.push(value);
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} else {
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result[key] = [currentValue, value];
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}
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}
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}
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// Reset reading key value pairs
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value = "";
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startingIndex = i;
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equalityIndex = i;
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shouldDecodeKey = false;
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shouldDecodeValue = false;
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keyHasPlus = false;
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valueHasPlus = false;
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// Check '='
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else if (c === 61) {
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if (equalityIndex <= startingIndex) {
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equalityIndex = i;
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}
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// If '=' character occurs again, we should decode the input.
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else {
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shouldDecodeValue = true;
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// Check '+', and remember to replace it with empty space.
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else if (c === 43) {
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if (equalityIndex > startingIndex) {
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valueHasPlus = true;
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} else {
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keyHasPlus = true;
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}
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// Check '%' character for encoding
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else if (c === 37) {
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if (equalityIndex > startingIndex) {
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shouldDecodeValue = true;
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} else {
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shouldDecodeKey = true;
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}
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}
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return result;
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}
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module.exports = parse;