- Part of the RegExp object, JavaScript's test() method offers the fastest way to check for matches in a string: think of it as the RegExp version of indexOf(), when it comes to searching for patterns.
Tip for examples on this page: the pattern "\s" (backslash and lowercase "s") matches whitespace, while "\S" (uppercase) matches any other character (letters, symbols, numbers, etc.)
- test() just returns a boolean true if it found a match, false otherwise. You can start by declaring a RegExp variable, or (our favorite approach) directly check for an anonymous pattern:
var str = document.getElementById("comments").value; // User commentsComments here:
if( /\S/.test(str) ) { // comments contain at least one letter/symbol/number
alert( "Thank you for your comments!" );
} else {
alert( "Please type some comments." );
document.getElementById("comments").focus();
} - In some cases, you'll want to check for a negative (that a string does NOT contain a pattern) - just prepend an exclamation mark "!" ("unary negation operator" - returns opposite of a boolean).
var zip = "*77845z"; // Expecting a 5-digit zip code...
if( ! /\D/.test(zip) ) // True if contains only numbers
document.dealerLocatorForm.submit();Note: you'll generally want to be more helpful by (for example) first removing all non-digits (/\D/g) from user inputs using the replace() method, and then only check for valid formats. FYI, a better way to check for a zip code would be the /^\d{5}$/ pattern.
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