how to know the type of variable in js code example

Example 1: javascript how to know type of variable

var foo = "Hello";
console.log(typeof foo); // string

Example 2: node js check type of variable

if (typeof i != "number") {
    console.log('This is not number');
}

Example 3: javascript check type of variable var

> typeof "foo"
"string"
> typeof true
"boolean"
> typeof 42
"number"