728x90
SMALL
#javascript
#javascript typeof operator
typeof Operator
typeof is an operator that returns the data type of a variable.
grammar
typeof variablevariable contains data or variables. Parentheses are allowed.
typeof(variable)
The returned values are:
- undefined: if the variable is not defined or has no value
- number : if the data type is number
- string : if the data type is a string
- boolean : if the data type is boolean
- object: if the data type is an object such as a function, array, etc.
- function: if the value of the variable is a function
- symbol : if the data type is symbol
for example
document.write( typeof 3 );or
var a = 3;
document.write( typeof a );will print number .
example
This is an example of outputting the data type while changing the value of the variable.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>JavaScript</title>
<style>
body {
font-family: Consolas, monospace;
font-size: 20px;
line-height: 1.6;
}
</style>
</head>
<body>
<script>
var a;
document.write( "typeof a : " + typeof a + "<br>" );
var a = 3;
document.write( "typeof a = 3: " + typeof a + "<br>" );
var a = 'Lorem';
document.write( "typeof a = 'Lorem' : " + typeof a + "<br>" );
var a = true;
document.write( "typeof a = true : " + typeof a + "<br>" );
var a = [ 'Lorem', 'Ipsum', 'Dolor' ];
document.write( "typeof a = [ 'Lorem', 'Ipsum', 'Dolor' ] : " + typeof a + "<br>" );
function a(){};
document.write( "typeof a(){} : " + typeof a + "<br>" );
var a = function(){};
document.write( "typeof a = function(){} : " + typeof a + "<br>" );
var a = Symbol();
document.write( "typeof a = Symbol() : " + typeof a + "<br>" );
</script>
</body>
</html>728x90
LIST
'Javascript' 카테고리의 다른 글
| [JavaScript] JavaScript/conditional statement/switch (0) | 2022.08.01 |
|---|---|
| [JavaScript] JavaScript / Conditionals / if, else if, else (0) | 2022.08.01 |
| [Javascript] JavaScript / operator / comparison operator (0) | 2022.07.29 |
| [Javascript] JavaScript / data type / string (0) | 2022.07.29 |
| [Javascript] Add a comment (0) | 2022.07.27 |