== vs ===
The == operator is known as the equality operator. It is used to compare the values of two operands, and if they are equal, it returns true. However, == does not compare the types of the operands, only their values. This can lead to unexpected results if you’re not careful. For example, 0 == false returns true, even though 0 is a number and false is a boolean.
The === operator is known as the strict equality operator. It works similarly to the == operator, but it also compares the types of the operands. If the types and values of the operands are equal, it returns true. If the types or values are different, it returns false. For example, 0 === false returns false.
So when should you use == and when should you use ===? In general, it’s a good idea to use === whenever possible. This is because === provides a more strict comparison, and it can help you avoid unexpected results. For example, if you’re checking for the existence of a variable, you might use if (variable !== undefined) instead of if (variable != undefined). The strict equality operator ensures that the variable is both defined and of the correct type.
However, there are some cases where you might want to use ==. For example, if you’re working with user input, you might want to use == to compare values, since users can enter values in many different formats. In this case, you might use something like if (inputValue == 42) instead of if (inputValue === 42).