The value null is often used to initialize variables that do not have any special meaning. You can assign it to a variable using the standard assignment statement:
var name = null;
The null value is special in that it is automatically converted to initial values of other data types. When used as a number it becomes 0, when used as a string it becomes "", and when used as a Boolean value it becomes false. Since the source of many JavaScript errors is uninitialized variables, one of the common debugging techniques is to initialize all new variables with a null value.
The JavaScript interpreter uses the null value on two occasions:
- Built-in functions return
null under certain circumstances.
- Non-existent properties evaluate to
null.
When checking for a null value, you should check if it is false:
if (!name) {
}
or if it is null:
if (name == null) {
}
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