Today #Day129 of #365DaysOfCode, Learning Essential JavaScript Interview Questions.
25. What will be the output of this code?
var x = 21;
var girl = function () {
console.log(x);
var x = 20;
};
girl ();
Neither 21, nor 20, the result is undefined
It’s because JavaScript initialization is not hoisted.
Why doesn’t it show the global value of 21?
The reason is that when the function is executed, it checks that there’s a local x variable present but doesn’t yet declare it, so it won’t look for global one.
var xx = 21;
var girl = function () {
console.log(xx);
xx = 20;
};
girl();
let y = 4;
const number2 = function number() {
console.log(y);
y = 5
console.log(y);
}
console.log(y);
number2();
26. What will this code print?
for (let i = 0; i < 5; i++) {
setTimeout(function () {
console.log(i);
}, i * 1000);
}
It will print 0 1 2 3 4, because we use let instead of var here. The variable i is only seen in the for loop’s block scope.
Conclusion
Learned and practiced Essential JavaScript Interview Questions involving topics like var with functions and setTimout.
Code
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