CODEWITHSUNDEEP
javascriptecmascript-6
user736893
user736893

Reputation:

Declaring variable with LET/ECMAscript 6 if it doesn't already exist

This works great:

var x = x || 3 //x = 3

This does not:

let y = y || 4 //Uncaught ReferenceError: y is not defined

My IDE () warns me on all usages of var, so I've been trying to avoid it (I assume this is current best practice). So what is the correct way to instantiate a variable only if it doesn't already exist?

Use Case: I am dynamically loading "widgets", which include an HTML, Javascript and CSS file. Each Javascript file has its own closure (widget = (function() {})()). I need to be able to "reload" these.

Upvotes: 2

Views: 84

Answers (1)

Brad
Brad

Reputation: 163262

Declare y first, then set its value in a different statement.

let y;
y = y || 4;

You can't declare with let or const multiple times, so you'll do that let declaration somewhere at the top of the scope you want it in.

Upvotes: 1

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