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Suggestion: support ||= compound assignment #20378

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Xample opened this issue Nov 30, 2017 · 2 comments
Closed

Suggestion: support ||= compound assignment #20378

Xample opened this issue Nov 30, 2017 · 2 comments
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Out of Scope This idea sits outside of the TypeScript language design constraints

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@Xample
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Xample commented Nov 30, 2017

Perhaps there is a good reason for this but I never understood why the compound assignment ||= is not part of js. This would be helpful to ensure a variable to be defined.

Given:

let a = {"key":"value"}

This would let us write:

a.key ||= "default";
a.anotherKey ||= "anotherDefault";

Instead of

a.key = a.key || "default";
a.anotherKey = a.anotherKey || "anotherDefault";

Of course we could have used

a = {...a, key:"default", anotherKey:"anotherDefault"}

But as a general case, this should work on any variable

let a;
a ||= "default";

instead of

let a;
a = a ||"default";
@DanielRosenwasser
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As much as I've personally wanted this, we really can't do this without it being added to ECMAScript itself, since adding syntactic features that aren't strictly on the type side doesn't fit into our design goals.

@DanielRosenwasser DanielRosenwasser added the Out of Scope This idea sits outside of the TypeScript language design constraints label Nov 30, 2017
@typescript-bot
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Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.

@microsoft microsoft locked and limited conversation to collaborators Jul 3, 2018
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@Xample @DanielRosenwasser @typescript-bot