How to Check if a String Contains Numbers in JavaScript
To check if a string contains numbers in JavaScript, call the test()
method on this regex: /\d/
. test()
will return true
if the string contains numbers. Otherwise, it will return false
.
For example:
function containsNumbers(str) {
return /\d/.test(str);
}
console.log(containsNumbers('hello123')); // true
console.log(containsNumbers('javascript')); // false
console.log(containsNumbers('3 apples')); // true
The RegExp test() method searches for a match between a regular expression and a string.
The /
and /
characters are used to start and end the regular expression.
The \d
metacharacter matches any digit (0
- 9
) in the string.
You can also use the [0-9]
to match digits. This pattern matches any number character between 0
and 9
.
function containsNumbers(str) {
return /[0-9]/.test(str);
}
console.log(containsNumbers('hello123')); // true
console.log(containsNumbers('javascript')); // false
console.log(containsNumbers('3 apples')); // true
You might find [0-9]
to be more readable than using \d
, especially if you're not very familiar with special characters in regular expressions.
Check if string contains only numbers
To check if the string contains only numbers, we'll have to use a different regular expression - ^\d+$
:
function containsOnlyNumbers(str) {
return /^\d+$/.test(str);
}
console.log(containsOnlyNumbers('hello123')); // false
console.log(containsOnlyNumbers('3453')); // true
console.log(containsOnlyNumbers('3 apples')); // false
The ^
character marks the beginning of the string input, and the $
character marks the end of it.
Adding the +
character after the \d
makes regex match one or more occurrences of the \d
pattern.
So the regex matches a string starting and ending with a consecutive sequence of digits.
As we did before, we could replace \d
with [0-9]
here:
function containsOnlyNumbers(str) {
return /^[0-9]+$/.test(str);
}
console.log(containsOnlyNumbers('hello123')); // false
console.log(containsOnlyNumbers('3453')); // true
console.log(containsOnlyNumbers('3 apples')); // false
The String match() method
We can use the String
match()
method in place of RegExp
test()
to check if a string contains numbers
function containsNumbers(str) {
return Boolean(str.match(/\d/));
}
console.log(containsNumbers('hello123')); // true
console.log(containsNumbers('javascript')); // false
console.log(containsNumbers('3 apples')); // true
The String match() method returns an array of all the matches of a regular expression in a string. If there are no matches, it returns null
.
function containsNumbers(str) {
return str.match(/\d/);
}
console.log(containsNumbers('hello123'));
// [ '1', index: 5, input: 'hello123', groups: undefined ]
console.log(containsNumbers('javascript')); // null
console.log(containsNumbers('3 apples'));
// [ '3', index: 0, input: '3 apples', groups: undefined ]
We pass the result of match()
to the Boolean()
constructor to convert it to a Boolean
value. Boolean()
converts truthy values to true
, and falsy values to false
.
In JavaScript, there are six falsy values: undefined
, null
, NaN
, 0
, ''
(empty string), and false
. Every other value is truthy.
console.log(Boolean(undefined)); // false
console.log(Boolean(['number60'])); // true
console.log(Boolean(null)); // false
console.log(Boolean(5)); // true
See also
- How to Check if a String Contains Only Numbers in JavaScript
- How to Remove a Query String From a URL in JavaScript
- How to Remove All Classes From an Element With JavaScript
- How to Capitalize the First Letter of Each Word in an Array in JavaScript
- How to Convert XML to JSON in JavaScript
- How to Subtract 6 Months From a Date in JavaScript