The typeof operator is a unary operator that is placed before its single operand, which can be of any type. Its value is a string indicating the data type of the operand. The typeof operator evaluates to "number", "string" or "boolean" if its operand is a number, string, or boolean value and returns true or false based on the evaluation.
Here is a list of the return values for the typeof Operator.
| Type | String Returned by typeof |
|---|---|
| Number | "number" |
| String | "string" |
| Boolean | "boolean" |
| object | "object" |
| Function | "function" |
| Undefined | "undefined" |
| Null | "object" |
Example
The following code shows how to implement typeof operator −
<html>
<body>
<script>
var a = 10;
var b = "String";
var linebreak = "<br />";
result = (typeof b == "string" ? "B is String" : "Bis Numeric");
document.write("Result => ");
document.write(result);
document.write(linebreak);
result = (typeof a == "string" ? "A is String" : "Ais Numeric");
document.write("Result => ");
document.write(result);
document.write(linebreak);
</script>
</body>
</html>