How to use let (or other JS 1.7 features) in the web console?

Question

I was wanting to test some things with let statement in the console, but I ran into a problem - it isn't supported in Firefox or Chromium. I know it's supported, if you set the javascript version in a script tag, but is there any option that will let you make sure the latest version of Javascript is enabled in the web console (or Scratchpad) of Firefox and/or Chromium?

Firefox already supports it in the Web console. For Chromium, see http://stackoverflow.com/a/17253177/938089. — Rob W, Jul 07 '13 at 10:57

score 2 · Accepted Answer · edited Jul 07 '13 at 10:53

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Works for me in the Firefox console.

Cmd + Shift + K to bring up the console and:

let x = 3; undefined x 3

edited Jul 07 '13 at 10:53

Rob W

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answered Jul 07 '13 at 01:41

Interesting. I tried `let x=3 { console.log(x); }` and it doesn't work. – NoBugs Jul 11 '13 at 05:07
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@NoBugs you need to wrap the x=3 in parens: "let (x=3){console.log(x)}" – Jul 19 '13 at 23:26

score 0 · Answer 2 · edited May 23 '17 at 12:17

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I think there's no such thing as a window.version or something like that... the common way is by checking like posted in Detect version of JavaScript

or even better heck out Modernizr, which is a great library that does feature detection for you.

edited May 23 '17 at 12:17

Community

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answered Jul 06 '13 at 03:18

Rafael Fontes

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Thank, but I know it supports JS1.7, the question is, how to use it without making a new script tag in a document, with the `type="application/javascript;version=1.7"` attribute. – NoBugs Jul 06 '13 at 04:46

score 0 · Answer 3 · answered Mar 24 '14 at 14:35

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In Chrome you have to activate JavaScript Harmony,"chrome://flags" enable-javascript-harmony

and use the strict mode "use strict";.

Here's a simple example:

"use strict";
let square = "trololo";
console.log(square);

answered Mar 24 '14 at 14:35

Walter Fuchs

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How to use let (or other JS 1.7 features) in the web console?

3 Answers3