How to check if a character is a letter or a number in javascript? - Stack Overflow

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I am new to javascript I'm trying to check user entered the alphabet or a number. if the user enters "A" it shows Alphabet it's ok but if the user enters "1" I want to show Number but its show alphabet. where i done wrong. Thanks Advance

function CHECKCHARATCTER(Letter) {
    if (Letter.length <= 1) {
      if ((64 < Letter.charCodeAt(0) < 91) || (96 < Letter.charCodeAt(0) < 123)) {
        return "Alphabhate";
      }
      else if (47 < Letter.charCodeAt(0) < 58) {
        return "NUMBER";
      }
      else { return "Its NOt a NUMBER or Alphabets"; }
    }
    else { return ("Please enter the single character"); }
}
a = prompt("enter the number or Alphabhate");
alert(typeof (a));
b = CHECKCHARATCTER(a);
alert(b);

I am new to javascript I'm trying to check user entered the alphabet or a number. if the user enters "A" it shows Alphabet it's ok but if the user enters "1" I want to show Number but its show alphabet. where i done wrong. Thanks Advance

function CHECKCHARATCTER(Letter) {
    if (Letter.length <= 1) {
      if ((64 < Letter.charCodeAt(0) < 91) || (96 < Letter.charCodeAt(0) < 123)) {
        return "Alphabhate";
      }
      else if (47 < Letter.charCodeAt(0) < 58) {
        return "NUMBER";
      }
      else { return "Its NOt a NUMBER or Alphabets"; }
    }
    else { return ("Please enter the single character"); }
}
a = prompt("enter the number or Alphabhate");
alert(typeof (a));
b = CHECKCHARATCTER(a);
alert(b);

• javascript

Share Improve this question Follow edited Feb 20, 2020 at 8:24 Balaj Khan 2,58022 gold badges2020 silver badges3030 bronze badges asked Feb 19, 2020 at 14:29 Velugoti VenkateswarluVelugoti Venkateswarlu 21333 silver badges66 bronze badges 1

• 3 You can't do a < b < c, you need a < b && b < c instead. – user5734311 Commented Feb 19, 2020 at 14:32

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 3

Here:

if (64 < Letter.charCodeAt(0) < 91) //...

JS isn't Python. You can't simply do a < b < c, you need to explicitly use the logical && operator: (a < b) && (b < c).

You can use regular expressions. Please have a look at regular expressions. It will be very helpful.
function checkAlphaNum(char) {
    let alphaReg = new RegExp(/^[a-z]/i);
    let numReg = new RegExp(/^[0-9]/);
    if(alphaReg.test(char)) {
        return "ALPHABET";
    } else if(numReg.test(char)) {
        return "NUMBER";
    } else {
        return "OTHER";
    }
}

console.log("Output : ", checkAlphaNum('A'));
console.log("Output : ", checkAlphaNum(1));

I modified you conditions as it's shown in the following code. Also you can check it out here

function CHECKCHARATCTER(Letter){
    if (Letter.length <= 1)
    {
        if (Letter.toUpperCase() != Letter.toLowerCase()) { 
            return "Alphabet";
        }
        else if (!isNaN( Letter)) {
            return "Number";
        } else{ 
            return "Its Not a Number or Alphabet";
        }
    }
    else { 
        return("Please enter the single character");
    }
}
input = prompt("enter the Number or Alphabet");
output = CHECKCHARATCTER(input);
alert(output);

I am new to javascript I'm trying to check user entered the alphabet or a number. if the user enters "A" it shows Alphabet it's ok but if the user enters "1" I want to show Number but its show alphabet. where i done wrong. Thanks Advance

function CHECKCHARATCTER(Letter) {
    if (Letter.length <= 1) {
      if ((64 < Letter.charCodeAt(0) < 91) || (96 < Letter.charCodeAt(0) < 123)) {
        return "Alphabhate";
      }
      else if (47 < Letter.charCodeAt(0) < 58) {
        return "NUMBER";
      }
      else { return "Its NOt a NUMBER or Alphabets"; }
    }
    else { return ("Please enter the single character"); }
}
a = prompt("enter the number or Alphabhate");
alert(typeof (a));
b = CHECKCHARATCTER(a);
alert(b);

I am new to javascript I'm trying to check user entered the alphabet or a number. if the user enters "A" it shows Alphabet it's ok but if the user enters "1" I want to show Number but its show alphabet. where i done wrong. Thanks Advance

function CHECKCHARATCTER(Letter) {
    if (Letter.length <= 1) {
      if ((64 < Letter.charCodeAt(0) < 91) || (96 < Letter.charCodeAt(0) < 123)) {
        return "Alphabhate";
      }
      else if (47 < Letter.charCodeAt(0) < 58) {
        return "NUMBER";
      }
      else { return "Its NOt a NUMBER or Alphabets"; }
    }
    else { return ("Please enter the single character"); }
}
a = prompt("enter the number or Alphabhate");
alert(typeof (a));
b = CHECKCHARATCTER(a);
alert(b);

• javascript

Share Improve this question Follow edited Feb 20, 2020 at 8:24 Balaj Khan 2,58022 gold badges2020 silver badges3030 bronze badges asked Feb 19, 2020 at 14:29 Velugoti VenkateswarluVelugoti Venkateswarlu 21333 silver badges66 bronze badges 1

• 3 You can't do a < b < c, you need a < b && b < c instead. – user5734311 Commented Feb 19, 2020 at 14:32

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 3

Here:

if (64 < Letter.charCodeAt(0) < 91) //...

JS isn't Python. You can't simply do a < b < c, you need to explicitly use the logical && operator: (a < b) && (b < c).

You can use regular expressions. Please have a look at regular expressions. It will be very helpful.
function checkAlphaNum(char) {
    let alphaReg = new RegExp(/^[a-z]/i);
    let numReg = new RegExp(/^[0-9]/);
    if(alphaReg.test(char)) {
        return "ALPHABET";
    } else if(numReg.test(char)) {
        return "NUMBER";
    } else {
        return "OTHER";
    }
}

console.log("Output : ", checkAlphaNum('A'));
console.log("Output : ", checkAlphaNum(1));

I modified you conditions as it's shown in the following code. Also you can check it out here

function CHECKCHARATCTER(Letter){
    if (Letter.length <= 1)
    {
        if (Letter.toUpperCase() != Letter.toLowerCase()) { 
            return "Alphabet";
        }
        else if (!isNaN( Letter)) {
            return "Number";
        } else{ 
            return "Its Not a Number or Alphabet";
        }
    }
    else { 
        return("Please enter the single character");
    }
}
input = prompt("enter the Number or Alphabet");
output = CHECKCHARATCTER(input);
alert(output);

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