not equal in javascript

The inequality (!=) operator in JavaScript is a commonly used operator used to compare whether two values ​​are equal. Corresponds to the equals (==) operator. So in the actual development process, how should we correctly use the inequality operator in JavaScript?

First of all, we need to clarify the definition of the not equal operator in JavaScript. The inequality operator is used when comparing two values. Returns true if the two values ​​are not equal; returns false if they are equal. Two values ​​can be of different types, but will be coerced to the same type for comparison. If one value is null and the other value is undefined, they are equal.

Because JavaScript is a weakly typed language, implicit conversion of data types may occur. Therefore, we need to pay special attention to the implicit type conversion problems that may arise when using the inequality operator. For example:

0 != "" // true
false != 0 // false
false != "" // true

in the first comparison expression , the empty string is converted to the number 0, so 0 and the empty string are not equal. In the second comparison expression, false is converted to the number 0, so 0 and false are equal. In the third comparison expression, the empty string is converted to the Boolean value false, so false and the empty string are not equal.

Therefore, when using the inequality operator, we should try our best to ensure that the data types of the two values ​​are the same to avoid implicit type conversion problems.

In addition, when comparing two objects, the inequality operator compares their reference addresses instead of the properties of the objects. Therefore, two objects are not equal even if they have the same properties but are different object instances. For example:

var obj1 = {

name: "Tom"

};
var obj2 = {

name: "Tom"

};
console.log(obj1 != obj2); // true

Although objects obj1 and obj2 have the same attribute name and the attribute values ​​are the same, they are different object instances and their reference addresses are also different, so they are not equal to what the operator returns. The result is true.

Finally, when using the inequality operator, we should pay attention to some potential performance issues. Because the inequality operator undergoes implicit type conversion, its performance may be affected. For a large number of comparison operations, we can use the equal to (===) operator instead of the not equal to operator. This can avoid the problem of implicit type conversion and improve the performance of the code.

To sum up, the inequality operator in JavaScript is a commonly used operator, but we need to pay attention to the implicit type conversion problems that may occur when using it, and try to ensure that the two comparisons are values ​​have the same data type. In addition, we should also note that when performing a large number of comparison operations, using the equal operator can improve the performance of the code and avoid implicit type conversion problems.

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