Validating user input is an essential aspect of Web Development. As a developer, when we are playing with the numeric inputs provided by the end-user, it is quite important to ensure that the input provided by the user is in the correct format. If the text field is expecting a decimal number and the user is entering the alphabetical value, then it should be handled properly and validated. JavaScript provides a built-in method called “isNumeric” that can be used to validate decimal numbers. The “isNumeric” method can be used to check wheater ta value is numeric or not. One argument is taken by the isNumeric function, which is “value“.
The general syntax for the “isNumeric” function is stated below:
Syntax:
function isNumeric(value) {
return /^-?\d+(\.\d+)?$/.test(value);
}
The function returns the Boolean value: “true” if the value is numeric, else the “false” value will be returned.
Examples 1:Validating a Decimal Number
Javascript
function isNumeric(value) { return /^-?\d+(\.\d+)?$/.test(value); } const value = "3.14"; const isNumber = isNumeric(value); console.log(isNumber); |
Output:
true
Explanation: In this example, the “isNumeric” function/method is used to validate the value “3.14“. The method returns “true” because the “3.14” value is a valid decimal number. The code prints the result “true” in the console.
Example 2: Validating a non-numeric value
Javascript
function isNumeric(value) { return /^-?\d+(\.\d+)?$/.test(value); } const value = "hello"; const isNumber = isNumeric(value); console.log(isNumber); |
Output:
false
Explanation: In this example, the “isNumeric” function is used to validate the value “hello“. The function returns “false” because “hello” is not a valid decimal number. The code displays the result as “false” in the console.
