w3resource

JavaScript test() Method: RegExp Object

Description

The test() method of the RegExp executes a search for a match between a regular expression and a specified string. Returns true or false.

Version

Implemented in JavaScript 1.2

Syntax

Regexp.test(str)

Parameter

RegExp: The name of the regular expression.

str: The string against which to match the regular expression.

Example:

The following web document demonstrates how the test() method can be used.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>JavaScript Regexp test Method : Example-1</title>
</head>
<body>
<h1 style="color: red">JavaScript Regexp test Method</h1>
<hr />
<script type="text/javascript">
//This is done to make the following JavaScript code compatible to XHTML. <![CDATA[
// Create a new RegExp object.
newRe = new RegExp('Fox','g')
// Define a string.
str1 = 'The Quick Brown Fox Jumps Over The Lazy Dog';
// Check whether regular expression exists in the string.
if (newRe.test(str1))
{
document.write("'Fox' is found in "+str1);
}
//]]>
</script>
</body>
</html>

View the example in the browser

Supported Browser

Internet Explorer 7 Firefox 3.6 Google Chrome 7 Safari 5.0.1 Opera 10
Yes Yes Yes Yes Yes

See also:

JavaScript Core objects, methods, properties.

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Next: JavaScript toSource() Method: RegExp Object



JavaScript: Tips of the Day

JavaScript: semicolon (;)

function nums(a, b) {
  if (a > b) console.log('a is bigger');
  else console.log('b is bigger');
  return;
  a + b;
}

console.log(nums(4, 2));
console.log(nums(1, 2));

In JavaScript, we don't have to write the semicolon (;) explicitly, however the JavaScript engine still adds them after statements. This is called Automatic Semicolon Insertion. A statement can for example be variables, or keywords like throw, return, break, etc.
Here, we wrote a return statement, and another value a + b on a new line. However, since it's a new line, the engine doesn't know that it's actually the value that we wanted to return. Instead, it automatically added a semicolon after return. You could see this as:

return;
a + b;
This means that a + b is never reached, since a function stops running after the return keyword. If no value gets returned, like here, the function returns undefined. Note that there is no automatic insertion after if/else statements!

Ref: https://bit.ly/3jFRBje