Small Discussion about Javascript(ECMASCRIPT 6) Variable & Scoping ?

Question

ES(ECMASCRIPT) 6 provides two new ways of declaring variables: let and const, which mostly replace the ES5 way of declaring variables, var.

LET

let works similarly to var, but the variable it declares is block-scoped, it only exists within the current block. var is function-scoped.

function order(x, y) {
    if (x > y) { // (A)
        let tmp = x;
        x = y;
        y = tmp;
    }
    console.log(tmp===x); // ReferenceError: tmp is not defined
    return [x, y];
}

CONST
const works like let, but the variable you declare must be immediately initialized, with a value that can’t be changed afterwards.

const allows you to declare a single assignment variable lexically bound. 

const foo;
    // SyntaxError: missing = in const declaration

const bar = 123;
bar = 456;
    // TypeError: `bar` is read-only

VAR
With const and let, there is no more space for var anymore.

 

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