Encode HTML Entities in JavaScript

var Title = $('<textarea />').html("Chris' corner").text();console.log(Title);

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Javascript encode HTML entities on server

Since I asked this question, I learned JavaScript and AJAX. So, my suggestion will be using AJAX and JSON for communication between browser and server-side.

Convert special characters to HTML in JavaScript

You need a function that does something like

return mystring.replace(/&/g, "&").replace(/>/g, ">").replace(/</g, "<").replace(/"/g, """);

But taking into account your desire for different handling of single/double quotes.

Encode HTML entities

Basically you should encode your html entities into html as such:

var encodedStr = data['1']['result']['content'];
var a = $("#content").html(encodedStr).text();

Then get the encoded text and apply it as html() as such:

$("#content").html(a);

That should work.

Demo: http://jsbin.com/ihadam/9/edit

Unescape HTML entities in JavaScript?

EDIT: You should use the DOMParser API as Wladimir suggests, I edited my previous answer since the function posted introduced a security vulnerability.

The following snippet is the old answer's code with a small modification: using a textarea instead of a div reduces the XSS vulnerability, but it is still problematic in IE9 and Firefox.

function htmlDecode(input){
  var e = document.createElement('textarea');
  e.innerHTML = input;
  // handle case of empty input
  return e.childNodes.length === 0 ? "" : e.childNodes[0].nodeValue;
}

htmlDecode("<img src='myimage.jpg'>"); 
// returns "<img src='myimage.jpg'>"

Basically I create a DOM element programmatically, assign the encoded HTML to its innerHTML and retrieve the nodeValue from the text node created on the innerHTML insertion. Since it just creates an element but never adds it, no site HTML is modified.

It will work cross-browser (including older browsers) and accept all the HTML Character Entities.

EDIT: The old version of this code did not work on IE with blank inputs, as evidenced here on jsFiddle (view in IE). The version above works with all inputs.

UPDATE: appears this doesn't work with large string, and it also introduces a security vulnerability, see comments.

A plain JavaScript way to decode HTML entities, works on both browsers and Node

There are many similar questions and useful answers in stackoverflow but I can't find a way works both on browsers and Node.js. So I'd like to share my opinion.

For html codes like   < > ' and even Chinese characters.

I suggest to use this function. (Inspired by some other answers)

function decodeEntities(encodedString) {
    var translate_re = /&(nbsp|amp|quot|lt|gt);/g;
    var translate = {
        "nbsp":" ",
        "amp" : "&",
        "quot": "\"",
        "lt"  : "<",
        "gt"  : ">"
    };
    return encodedString.replace(translate_re, function(match, entity) {
        return translate[entity];
    }).replace(/&#(\d+);/gi, function(match, numStr) {
        var num = parseInt(numStr, 10);
        return String.fromCharCode(num);
    });
}

This implement also works in Node.js environment.

decodeEntities("哈哈 '这个'&"那个"好玩<>") //哈哈 '这个'&"那个"好玩<>

As a new user, I only have 1 reputation :(

I can't make comments or answers to existing posts so that's the only way I can do for now.

Edit 1

I think this answer works even better than mine. Although no one gave him up vote.

How to encode html tag entities - JavaScript

Using String prototype

A possible solution is defining a replaceAll function, e.g. in the prototype of String:

String.prototype.replaceAll = function(search, replace) {
    return this.replace(new RegExp('[' + search + ']', 'g'), replace);
};

After this, you only need to iterate over the properties of charsToReplace:

for (var prop in charsToReplace) {
   if (charsToReplace.hasOwnProperty(prop)) {
       str = str.replaceAll(prop, charsToReplace[prop]));
   }
}

The final str can be assigned to the innerHTML.

Using normal function

If for some reason, you do not want to mess with the prototype, you may define a normal JavaScript function for the same task:

var replaceAll = function (str, search, replace) {
    return str.replace(new RegeExp('[' + search + ']', 'g'), replace);
}

This works really the same way, you just need to pass the string instance to it:

str = replaceAll(str, prop, charsToReplace[prop]));

Another approach

If you would use these methods often, you might consider storing the regex patterns in your charsToReplace object, like this:

var charsToReplace = {
    '&': {
        pattern: new RegExp('[' + '&' + ']', 'g'),
        replace: '&'
    }
    ...
}

So your replaceAll function would look like this:

var replaceAll = function (str, replacement) {
    return str.replace(replacement.pattern, replacement.replace);
}

This way you would not need to recreate the regular expressions every time, which could save some processing time.

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