检查输入是否以特定字符结尾

Question

I have this basic input field:

<input type="text" name="one" />

How can I make sure user ends the input value with a specific character, for example comma (,) before running server-side code?

Example:

"hello world" (invalid)

"hello world," (valid)

Answer 1

You can use includes()

 var str = 'hello world,' if (str.includes(',',-1)) alert ('valid') 

Note that includes is an es6 feature and will only work in modern browsers, see the link I posted above for further information and a polyfill.

Answer 2

This can be done using HTML5's input pattern attribute, which validates input with a regular expression. The form will not be allowed to submit in modern browsers that support this attribute - but you should always validate user input server-side as well.

 input:valid { background: lime; } input:invalid { background: red; } 

 <input type="text" pattern="(.+?),$"> 

The CSS used in this example is purely to display when the input is valid (green).

Answer 3

Why don't you just use HTML5 pattern validation? It's very easy and no Javascript to maintain.

Demo Snippet:

 <form> <input type="text" name="one" pattern=".*,$" /> <input type="submit" value="Submit" /> </form> 

Answer 4

HTML:

<form name="myForm">
  <input type="text" name="one" onkeypress="validateForm()">
  <input type="submit">
</form>

JS:

function validateForm() {
    var x = document.forms["myForm"]["one"].value;
    if(x.charAt(x.length-1) == ','){
    console.log("true");
    }else{
   console.log("false");
    }
}

Answer 5

There javascript function endsWith which check is string ends with certain character

 var chr  = "Hello world,";
    if(chr.endsWith(",") {

    }else{

    }

as kenny said it wont worked on IE..MDN has provided protoype function for this function

if (!String.prototype.endsWith) {
  String.prototype.endsWith = function(searchString, position) {
      var subjectString = this.toString();
      if (typeof position !== 'number' || !isFinite(position) || Math.floor(position) !== position || position > subjectString.length) {
        position = subjectString.length;
      } 
      position -= searchString.length;
      var lastIndex = subjectString.indexOf(searchString, position);
      return lastIndex !== -1 && lastIndex === position;
  };
}

Answer 6

The most basic method is similar to Marcin C's:

function endsWith(str, end) {
    var $len = str.length,
    $endlen = end.length;
    if (substr($len - $endlen, $endlen) === end) {
        return true;
    } else {
        return false;
    }
}

Answer 7

I would add an ID, in order to easily extract the value:

var textInputValue = document.getElementById("myIdHere").value; 

Then use regex to see if it matches your pattern:

if( textInputValue.match(/,$/) ){
     alert("the input is valid!");
} else {
     alert("sorry, invalid input"); 
}

Here is a fiddle: http://jsfiddle.net/ybsuyx6e/

Answer 8

/,$/.test("hello world,") // true