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Mar 11th, 2018

JavaScript 'let' vs 'var'

'let' in JavaScript (ES6) allows you to declare variables with block scope rather than function scope (which is what 'var' does):

function foo()
{
    var x = 5;
    let y = 5;

    if (/*something*/)
    {
        var x = 10;     // Oh no! This is the same x from above!
        let y = 10;     // Brand new variable scoped to this block only
    }

    console.log(x);     // 10
    console.log(y);     // 5
}

All 'var' declarations of the same name within a function map to the same variable - kinda silly, right? Especially if you come from a language where block scoping is the norm.

Stick with 'let' and avoid the confusion.