Check whether an input string contains a number in javascript

Question

My end goal is to validate an input field. The input may be either alphabetic or numeric.

Answer 1

If I'm not mistaken, the question requires "contains number", not "is number". So:

function hasNumber(myString) {
  return /\d/.test(myString);
}

Answer 2

You can do this using javascript. No need for Jquery or Regex

function isNumeric(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

While implementing

var val = $('yourinputelement').val();
if(isNumeric(val)) { alert('number'); } 
else { alert('not number'); }

Update: To check if a string has numbers in them, you can use regular expressions to do that

var matches = val.match(/\d+/g);
if (matches != null) {
    alert('number');
}

Answer 3

This is what you need.

      var hasNumber = /\d/;   
      hasNumber.test("ABC33SDF");  //true
      hasNumber.test("ABCSDF");  //false 

Answer 4

function validate(){    
    var re = /^[A-Za-z]+$/;
    if(re.test(document.getElementById("textboxID").value))
       alert('Valid Name.');
    else
       alert('Invalid Name.');      
}

Answer 5

It's not bulletproof by any means, but it worked for my purposes and maybe it will help someone.

var value = $('input').val();
 if(parseInt(value)) {
  console.log(value+" is a number.");
 }
 else {
  console.log(value+" is NaN.");
 }

Answer 6

Using Regular Expressions with JavaScript. A regular expression is a special text string for describing a search pattern, which is written in the form of /pattern/modifiers where "pattern" is the regular expression itself, and "modifiers" are a series of characters indicating various options.
         The character class is the most basic regex concept after a literal match. It makes one small sequence of characters match a larger set of characters. For example, [A-Z] could stand for the upper case alphabet, and \d could mean any digit.

From below example

• contains_alphaNumeric « It checks for string contains either letter or number (or) both letter and number. The hyphen (-) is ignored.
• onlyMixOfAlphaNumeric « It checks for string contain both letters and numbers only of any sequence order.

Example:

function matchExpression( str ) {
    var rgularExp = {
        contains_alphaNumeric : /^(?!-)(?!.*-)[A-Za-z0-9-]+(?<!-)$/,
        containsNumber : /\d+/,
        containsAlphabet : /[a-zA-Z]/,

        onlyLetters : /^[A-Za-z]+$/,
        onlyNumbers : /^[0-9]+$/,
        onlyMixOfAlphaNumeric : /^([0-9]+[a-zA-Z]+|[a-zA-Z]+[0-9]+)[0-9a-zA-Z]*$/
    }

    var expMatch = {};
    expMatch.containsNumber = rgularExp.containsNumber.test(str);
    expMatch.containsAlphabet = rgularExp.containsAlphabet.test(str);
    expMatch.alphaNumeric = rgularExp.contains_alphaNumeric.test(str);

    expMatch.onlyNumbers = rgularExp.onlyNumbers.test(str);
    expMatch.onlyLetters = rgularExp.onlyLetters.test(str);
    expMatch.mixOfAlphaNumeric = rgularExp.onlyMixOfAlphaNumeric.test(str);

    return expMatch;
}

// HTML Element attribute's[id, name] with dynamic values.
var id1 = "Yash", id2="777", id3= "Yash777", id4= "Yash777Image4"
    id11= "image5.64", id22= "55-5.6", id33= "image_Yash", id44= "image-Yash"
    id12= "_-.";
console.log( "Only Letters:\n ", matchExpression(id1) );
console.log( "Only Numbers:\n ", matchExpression(id2) );
console.log( "Only Mix of Letters and Numbers:\n ", matchExpression(id3) );
console.log( "Only Mix of Letters and Numbers:\n ", matchExpression(id4) );

console.log( "Mixed with Special symbols" );
console.log( "Letters and Numbers :\n ", matchExpression(id11) );
console.log( "Numbers [-]:\n ", matchExpression(id22) );
console.log( "Letters :\n ", matchExpression(id33) );
console.log( "Letters [-]:\n ", matchExpression(id44) );

console.log( "Only Special symbols :\n ", matchExpression(id12) );

Out put:

Only Letters:
  {containsNumber: false, containsAlphabet: true, alphaNumeric: true, onlyNumbers: false, onlyLetters: true, mixOfAlphaNumeric: false}
Only Numbers:
  {containsNumber: true, containsAlphabet: false, alphaNumeric: true, onlyNumbers: true, onlyLetters: false, mixOfAlphaNumeric: false}
Only Mix of Letters and Numbers:
  {containsNumber: true, containsAlphabet: true, alphaNumeric: true, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: true}
Only Mix of Letters and Numbers:
  {containsNumber: true, containsAlphabet: true, alphaNumeric: true, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: true}
Mixed with Special symbols
Letters and Numbers :
  {containsNumber: true, containsAlphabet: true, alphaNumeric: false, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: false}
Numbers [-]:
  {containsNumber: true, containsAlphabet: false, alphaNumeric: false, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: false}
Letters :
  {containsNumber: false, containsAlphabet: true, alphaNumeric: false, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: false}
Letters [-]:
  {containsNumber: false, containsAlphabet: true, alphaNumeric: true, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: false}
Only Special symbols :
  {containsNumber: false, containsAlphabet: false, alphaNumeric: false, onlyNumbers: false, onlyLetters: false, mixOfAlphaNumeric: false}

java Pattern Matching with Regular Expressions.

Answer 7

You can do this using javascript. No need for Jquery or Regex

function isNumeric(n) 
{
  return !isNaN(n);
}

Answer 8

To test if any char is a number, without overkill❓, to be adapted as need.

const s = "EMA618"

function hasInt(me){
  let i = 1,a = me.split(""),b = "",c = "";
  a.forEach(function(e){
   if (!isNaN(e)){
     console.log(`CONTAIN NUMBER «${e}» AT POSITION ${a.indexOf(e)} => TOTAL COUNT ${i}`)
     c += e
     i++
   } else {b += e}
  })
  console.log(`STRING IS «${b}», NUMBER IS «${c}»`)
  if (i === 0){
    return false
    // return b
  } else {
    return true
    // return +c
  }
}


hasInt(s)

Answer 9

One way to check it is to loop through the string and return true (or false depending on what you want) when you hit a number.

function checkStringForNumbers(input){
    let str = String(input);
    for( let i = 0; i < str.length; i++){
              console.log(str.charAt(i));
        if(!isNaN(str.charAt(i))){           //if the string is a number, do the following
            return true;
        }
    }
}

Answer 10

parseInt provides integers when the string begins with the representation of an integer:

(parseInt '1a')  is  1

..so perhaps:

isInteger = (s)->
  s is (parseInt s).toString()  and  s isnt 'NaN'

(isInteger 'a') is false
(isInteger '1a') is false
(isInteger 'NaN') is false
(isInteger '-42') is true

Pardon my CoffeeScript.

Answer 11

I think it's simple and easy way to extract numbers and string.

str = "jdghj4874y6jfngvjbng"
let num = []
let strEx = []
for (i = 0; i < str.length; i++) {
  if (str[i] >= 0) {
    num.push(str[i])
  } else {
    strEx.push(str[i])
  }
}
console.log('nums:', JSON.stringify(num))
console.log('chars:', JSON.stringify(strEx))

Answer 12

This code also helps in, "To Detect Numbers in Given String" when numbers found it stops its execution.

function hasDigitFind(_str_) {
  this._code_ = 10;  /*When empty string found*/
  var _strArray = [];

  if (_str_ !== '' || _str_ !== undefined || _str_ !== null) {
    _strArray = _str_.split('');
    for(var i = 0; i < _strArray.length; i++) {
      if(!isNaN(parseInt(_strArray[i]))) {
        this._code_ = -1;
        break;
      } else {
        this._code_ = 1;
      }
    }

  }
  return this._code_;
}

Answer 13

Below code checks for same number, sequence number and reverse number sequence.

function checkNumSequnce(arrayNM2) {
    inseqCounter=1;
    continousSeq = 1;
    decsequenceConter = 1;
    var isequence = true;
    for (i=0;i<arrayNM2.length-1;i++) {
      j=i+1;
      if (arrayNM2[i] == arrayNM2[i+1]) { 
                if(inseqCounter > 1 || decsequenceConter > 1){
                    isequence =  false; break;
                }        
                 continousSeq++; 
                             
         }         
        else if (arrayNM2[j]- arrayNM2[i] == 1) {
            if(decsequenceConter > 1 || continousSeq > 1){
                isequence =  false; break;  
              }      
             inseqCounter++;               
                        
        } else if(arrayNM2[i]- arrayNM2[j] == 1){
              if(inseqCounter > 1 || continousSeq > 1){
                   isequence =  false; break;
               }
              decsequenceConter++;
        }else{
              isequence= false;
              break;
        }
  };

  console.log("isequence: "+ isequence); 

  };

Answer 14

We can check it by using !/[^a-zA-Z]/.test(e)
Just run snippet and check.

function handleValueChange() {
  if (!/[^a-zA-Z]/.test(document.getElementById('textbox_id').value)) {
      var x = document.getElementById('result');
      x.innerHTML = 'String does not contain number';
  } else {
    var x = document.getElementById('result');
    x.innerHTML = 'String does contains number';
  }
}

input {
  padding: 5px;
}

<input type="text" id="textbox_id" placeholder="Enter string here..." oninput="handleValueChange()">
<p id="result"></p>

Answer 15

Nobody has addressed the body of the question:

My end goal is to validate an input field. The input may be either alphabetic or numeric.

-- op

So here is a function that returns a boolean answer,
true if the passed input has a Number value OR a strictly alphabetic string value,
false otherwise:

const isAlphaOrNumeric = input => {
  if ('' === input.value.trim())
    return false // empty
    
  if (!Number.isNaN(Number(input.value)))
    return true //'number'

  return /^[a-zA-Z]+$/.test(input.value.trim()) // 'alphabetic'
}

const isAlphaOrNumeric = input => {
  if ('' === input.value.trim())
    return false

  if (!Number.isNaN(Number(input.value)))
    return true

  return /^[a-zA-Z]+$/.test(input.value.trim())
}

const f = document.querySelector('form')
const test = f.querySelector('[name="test"]')
const test2 = f.querySelector('[name="test2"]')
const test3 = f.querySelector('[name="test3"]')
f.onsubmit = e => {
  e.preventDefault()
  console.log(test.value, isAlphaOrNumeric(test))
  console.log(test2.value, isAlphaOrNumeric(test2))
  console.log(test3.value, isAlphaOrNumeric(test3))
}

<form>
  <input name="test" value="abc"><br>
  <input name="test2" value="-3.14"><br>
  <input name="test3" value="AFF4B3"><br>
  <button>
    check it
  </button>
</form>

Answer 16

Try this to check whether string has number or not.

'test123'.split('').reduce((result,ch) => ch.charCodeAt(0) >= 48 && ch.charCodeAt(0) <= 57), false);

Answer 17

You can also try lodash:

const isNumeric = number => 
  _.isFinite(_.parseInt(number)) && !_.isNaN(_.parseInt(number))