Equals

In Node.js we can compare things with two equals signs or three equals signs. There is a subtle difference here. But in most cases the two have the same effect.

With three equals signs, the types of the two variables must be equal. With two equals signs, a conversion may occur in the runtime.

Example

Here we have a string that stores digit characters (text). And we have a number that directly stores its integer value.

var text = "800";
var number = 800;

// Use type conversion with two equals.
if (text == number) {
    console.log("OK");
}

// Do not allow type conversion with 3 equals.
if (text === number) {
    console.log("Not reached");
}

// Use not equals with no type conversion.
if (text !== number) {
    console.log("OK 2");
}
OK
OK 2

In programming, we try to reduce the number of steps needed. The best practice remains as before: use three equals signs when possible. A possible conversion is eliminated.

With three equals signs, we compare both the type and the value of two variables. With two equals signs, only the values are compared—conversions may occur.