javascript var vs let
// var has function scope.
// let has block scope.
function func(){
if(true){
var A = 1;
let B = 2;
}
A++; // 2 --> ok, inside function scope
B++; // B is not defined --> not ok, outside of block scope
return A + B; // NaN --> B is not defined
}let: //only available inside the scope it's declared, like in "for" loop,
var: //accessed outside the loop "for"The let statement declares a block scope local variable, optionally initializing it to a value.
let x = 1;
if (x === 1) {
let x = 2;
console.log(x);
// expected output: 2
}
console.log(x);
// expected output: 1function run() {
var foo = "Foo";
let bar = "Bar";
console.log(foo, bar);
{
let baz = "Bazz";
console.log(baz);
}
console.log(baz); // ReferenceError
}
run();
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