How to check if JavaScript string contains a character

To find a character in a String has to use a includes() method in the JavaScript program. Another way to a string contains a certain character using a regular expression.

They include() method finds the “contains” character in whole string, it will return a true.

Example 1: Find a “t” character in the string.

<!DOCTYPE html> 
<html> 
<body> 
<p id="EHS"></p> 
<script> 
  
    var str = "EyeHunts JavaScript tutorial."; 
    var check = str.includes("t"); 
    document.getElementById("EHS").innerHTML = check; 
  
</script> 
  
</body> 
</html> 

Output: true

Example 2: Find a “z” char in string.

<!DOCTYPE html> 
<html> 
<body> 
<p id="EHS"></p> 
<script> 
  
    var str = "EyeHunts JavaScript tutorial."; 
    var check = str.includes("z"); 
    document.getElementById("EHS").innerHTML = check; 
  
</script> 
  
</body> 
</html> 

Output: false

Note: The includes() method is case sensitive, so Uppercase and Lowercase characters different.

Q: How to Javascript check if the string contains only a certain character?

Answer: Return true if a given string has only a certain character and any number of occurrences of that character.

The below example will pop-up an alert box with the result.

// checking for 's'
'ssssss' -> true
'sss s'  -> false
'so'     -> false
<!DOCTYPE html>
<html>

<script type="text/javascript">
window.onload = function(){
   document.getElementById('button').onclick = function(e){
      var a = document.getElementById("message").value;
                var result = new RegExp("^[s\s]+$").test(a);
                alert(result);
       return false;
   }
}
</script>

<body>


<div class="container">
    <form action="javascript:;" method="post" class="form-inline" id="form">
        <input type="text" id="message" class="input-medium" placeholder="Message" value="Hello, world!" />
   
        <button type="button" id="button" data-action="insert">Show</button>

    </form>
</div>
</body>
</html>

Output:

Javascript check if the string contains only a certain character

Q: How to check if a string contains [a-zA-Z] characters only?

Answer: No jQuery Needed, You can use a regex:

if (str.match(/[a-z]/i)) {
    // alphabet letters found
}

The i makes the regex case-insensitive. You could also do.

/[a-z]/.test(str.toLowerCase());

Do comment if you knew any other ways or have any doubts about this tutorial.

Note: The Examples are tested on Safari browser (Version 12.0.2) and Chrome.
OS: macOS 10.14 Mojave
Code: HTML 5 Version


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