在JavaScript中使用===进行字符串比较是否有意义？

Question

While it's clear how using the === operator for eg numbers is useful ( 0 , null and undefined all being falsy values, which can lead to confusion), I'm not sure if there are benefits to using === for string comparisons.

Some of my team mates use this operator for all comparisons, but does it really make sense? Is there at least some minor performance impact?

Answer 1

If you know the types are the same, then there's no difference in the algorithm between == and === .

That said, when I see == , I assume that I'm using it for its type coercion, which makes me stop and analyze the code.

When I see === I know that there's no coercion intended, so I don't need to give it a second thought.

In other words, I only use == if I intend for there to be some sort of type coercion.

Answer 2

It is considered good practice to always use === for comparisons in JavaScript. Since JavaScript is a dynamic language, it is possible that what you think are two strings could be variables with different types.

Consider the following:

var a = "2", b = 2;
a == b  // true
a === b // false

The only way to guarantee a false result in this case would be to use === when comparing the two values.