You need to know some tips in JS (DHTML) _ basic knowledge

You need to know some tips in JS (DHTML) that haven't updated the log these days. This article is just a bit of my own experience. I would like to give you some tips. If you have any questions, please leave a message below.

I. Equality Operators
In JS, the numbers not 0 are all true, except for a few special variables. For example, undefined, null, and. This is what we expect in most cases.
However, you should not ignore this full equality operator. Therefore, we need to strictly verify this. We can use the = full equality operator to view the following code:
// Some common verification results
Var foo = function (arg ){
If (! Arg ){
Alert ("normal false ");
} Else {alert ("true ");}
}
Foo (null); // false
Foo (false); // false
Foo (""); // false
Foo ("never-online"); // true
// Full equivalent Verification
Var foo = function (arg ){
If (arg = false ){
Alert ("false ");
} Else {alert ("not a false variable ")}
}
Foo (null); // not a false variable
Foo (false); // false
Foo (""); // not a false variable
Foo ("never-online"); // not a false variable

2. Application of Variable -- Remove Web page nesting
For example, if you want to embed baidu.com into your own iframe, the result is not what you want, because it has such a code
If (self! = Top) {top. location = self. location ;}
This Code indicates that if a webpage is nested (that is, frame technology is used, nesting is removed and the url in the frame is given to the top-level window)
This is a headache. For example, the above Code is also used in some free space. What if it is removed? With this code, nesting can be removed:
Script
Var location = 'Never-online ';
Script
The following describes why this code can be used to remove nesting:
We know that in JS variables, if the variables are like this