regular expressions<\/a> to check if a value is a number or not. Here is a regular expression to cover all integers.<\/p>\n\n\n\n^-?\\d+$<\/pre>\n\n\n\nHere is an example that uses the above expression to check whether a value is number or not.<\/p>\n\n\n\n
value = 123;
console.log(\/^-?\\d+$\/.test(value)); \/\/ output is true
value = -123;
console.log(\/^-?\\d+$\/.test(value)); \/\/ output is true<\/pre>\n\n\n\nThe above regular expression does not work for numbers with decimal points.<\/p>\n\n\n\n
value = -123.56;
console.log(\/^-?\\d+$\/.test(value)); \/\/ output is false<\/pre>\n\n\n\nIf you also want to cover numbers with decimal point then you need to modify your regular expression to the following.<\/p>\n\n\n\n
^-?\\d+(\\.\\d+)?$<\/pre>\n\n\n\nHere are a couple of examples to check if a value with decimal point is a number or not.<\/p>\n\n\n\n
value = -123.56;
console.log(\/^-?\\d+(\\.\\d+)?$\/.test(value)); \/\/ output is true<\/pre>\n\n\n\nJavaScript also uses numbers with scientific notations such as 1e3. If you want to check if these are also numbers then you need to use the following regular expression.<\/p>\n\n\n\n
^-?\\d+(\\.\\d+)?(e-?\\d+)?$<\/pre>\n\n\n\nHere is an example to check whether such a value is number or not.<\/p>\n\n\n\n
value = 1.23e4;
console.log(\/^-?\\d+(\\.\\d+)?(e-?\\d+)?$\/.test(value)); \/\/ output is true<\/pre>\n\n\n\nYou can convert the above checks into a function for convenience.<\/p>\n\n\n\n
value = 1.23;
function is_number(value) {
return \/^-?\\d+$\/.test(value);
}
console.log(is_number(value)); \/\/ output is false<\/pre>\n\n\n\n