How to check if a text input string on change has a number using Javascript

Question

Is there a way to check if a text input, on change, has a number in the string without using regex and only using just javascript?

For example (this may not be a good approach, I am unsure):

const passwordInput = document.querySelector("#password");
passwordInput.addEventListener("change", e => {
    if (e.target.value contains a number) {
        console.log("Must contain a number.")
    }
})

See stackoverflow.com/questions/5778020/… for solution. Please note that one digit is a "number". Just verify that this is what you want — Mulli
– Mulli, Commented Jun 5, 2020 at 18:51
[Off-topic]: you can use the input event instead of change for instant checks — FZs
– FZs, Commented Jun 5, 2020 at 19:14

FZs · Accepted Answer · 2020-06-05 19:45:49Z

1

You can iterate over it, and check each character, you can use !isNaN(x) to check if a x can be converted to a number, and x.trim() !== '' to filter out whitespaces (thanks to @Lain for pointing out that isNaN returns false for whitespaces):

function hasNumbers(string){
  return Array.prototype.some.call(string, c => !isNaN(c) && c.trim())
}

const passwordInput = document.querySelector("#password");
passwordInput.addEventListener("change", e => {
    if (hasNumbers(e.target.value)) {
        console.log("Contains a number.")
    } else {
        console.log("Doesn't contain a number.")
    }
})

<input id="password" >

edited Jun 5, 2020 at 19:45

answered Jun 5, 2020 at 18:58

FZs

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1 Comment

Lain Over a year ago

Sure: !isNaN(' ')

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