Why the equal sign is accepted between 'let' and name of the variable?-CodePudding

I accidentally wrote a weird declaration in my code

let = x = 5;

And it took me some time to actually notice it as it worked as expected (x was indeed 5). I wanted to ask why is that? Is it interpreted similarly as

let y = x = 5;

(just with the missing second variable) or has it some other function? It bothered me since and I can't seem to find an answer

CodePudding user response：

You assigned the value of 5 to both let and x:

let = x = 5;
console.log(let);
// Outputs 5

However, this doesn't interfere with the let keyword, and it still works as per usual.

CodePudding user response：

This is for backwards compatibility.

let was a valid variable name before it was added to the JavaScript language, and needs to remain so to avoid breaking old software.

let = 5;
console.log(let);

This isn't the case for code running in strict mode (which I strongly advise using if at all possible).

<script type="module">
let = 5;
console.log(let);
</script>