Discussion on: JavaScript Scopes

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The cost of this is added complexity to the language

One can argue about this :) I would say that let and const makes Javascript simpler and that var adds complexity to the language. Most developers expects variables to be blocked scoped. But then again you should really learn the language first and then the concept function scope shouldn't be a problem.

I'm using a linting rule to disallow the use of var in my code base because i see no advantage of using it.

On more case that is tricky with var is when deferring execution.

var functions = [];
for (var i=0;i<3;i++) {
    functions[i] = function() {
        console.log(i);
    }
}

functions[0](); // 3
functions[1](); // 3
functions[2](); // 3

xiaohuoni • Jul 10 '17

var functions = [];
for (var i=0;i<3;i++) {
functions[i] = function(i) {
console.log(i);
}(i)
}

functions0; // 0
functions1; // 1
functions2; // 2