Detect if a string is a number with regex

Andres Canavesi
Andrés Canavesi
Aug 28, 2020
How to know if a string is a number in JavaScript using a regular expression
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You can test this regex at https://regex101.com/

      

/**
 * It's not strictly the same than isNumber()
 *
 * @param text
 * @return true if the given text  is s number
 */
function isNumberText (text) {
    if (!text)  return false;
    // the value must be a number, including float and not empty.
    const reg = new RegExp('^-?\\d+\\.?\\d*$');
    return reg.test(text);
};

Examples

      
// it will return true on these cases
12
"12"
32.3
"43.4"

// false for these cases
"22a"
undefined
null
""
"1    2"
Photo by Nick Hillier on Unsplash
js regex util dev