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Basic use of Boolean objects in JavaScript programming_Basic knowledge

WBOY
WBOYOriginal
2016-05-16 15:35:051418browse

Boolean objects are used to convert non-Boolean values ​​into Boolean values ​​(true or false).

Check Boolean value
Checks whether a boolean object is true or false.
Source code example:

<!DOCTYPE html>
<html>
<body>
&#8203;
<script>
var b1=new Boolean(0);
var b2=new Boolean(1);
var b3=new Boolean("");
var b4=new Boolean(null);
var b5=new Boolean(NaN);
var b6=new Boolean("false");
&#8203;
document.write("0 is boolean "+ b1 +"<br>");
document.write("1 is boolean "+ b2 +"<br>");
document.write("An empty string is boolean "+ b3 + "<br>");
document.write("null is boolean "+ b4+ "<br>");
document.write("NaN is boolean "+ b5 +"<br>");
document.write("The string 'false' is boolean "+ b6 +"<br>");
</script>
&#8203;
</body>
</html>

Test results:

0 is boolean false
1 is boolean true
An empty string is boolean false
null is boolean false
NaN is boolean false
The string 'false' is boolean true

Create Boolean object
Boolean object represents two values: "true" or "false"
The following code defines a Boolean object named myBoolean: 

var myBoolean=new Boolean();

If the Boolean object has no initial value or its value is:

0
-0
null
""
false
undefined
NaN

Then the value of the object is false. Otherwise, its value is true (even when the argument is the string "false")!

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