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.
JavaScript notes. 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.
Start The two variables are considered equal with the "==" operator as the string is converted to a number.
Next The two variables are not equal here as they have different types. The inner block is not reached.
Finally This evaluates to true as the two values have unequal types. This operator tests both types and values.
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.
Summary. 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.
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This page was last updated on Dec 13, 2023 (edit).