Crockford 在 The Good Parts 中的“deentityify”方法真的有效吗？

Question

This particular code has been asked about twice before, but never was the question raised "does it actually do anything?". It appears in page 41 of Crockford's book.

Here is the syntactic sugar from earlier in the book:

Object.prototype = function (name, func){
    if(!this.prototype[name]){
    this.prototype[name] = func;
    }

and here is the deentityify methody:

String.method('deentityify', function ( ) {
    var entity = {
        quot: '"',
        lt: '<',
        gt: '>'
    };
    return function () {
        return this.replace(
            /&([^&;]+);/g,
            function (a, b) {
                var r = entity[b];
                return typeof r === 'string' ? r : a;
            }
        );
    };
}());

if in an editor your write something like:

document.writeln( '<">'.deentityify( ));

you'll see in the browser: however, if you type this in the browser: document.writeln( '<">');

you'll still see:

<">

I discovered that this method isn't actually replacing the entities when I attempted to use when pre-filling form data by setting the value field like this:

 var venueInput = document.createElement("input");           
        ...
        venueName = '<>&quot'; // for example
        venueInput.value = venueName.deentityify();
        form.appendChild(venueName);
        form.appendChild(venueInput);

Alert also show the entities aren't being replaced.

Can anyone help me see what I'm doing wrong? Thank you!

Answer 1

After fixing some mistakes of the code you shared it works like a charm:

 Object.prototype.method = function (name, func){ if(!this.prototype[name]){ this.prototype[name] = func; } } String.method('deentityify', function ( ) { var entity = { quot: '"', lt: '<', gt: '>' }; return function() { return this.replace( /&([^&;]+);/g, function (a, b) { var r = entity[b]; return typeof r === 'string' ? r : a; } ); }; }()); var venueInput = document.createElement("input"); var label = document.createElement("label"); venueName = '&lt;&gt;&quot;'; // for example venueInput.value = venueName.deentityify(); label.innerHTML = venueName; document.getElementById('form').appendChild(label); document.getElementById('form').appendChild(venueInput);

 <div id="form"></div>

Answer 2

Here is the syntactic sugar from earlier in the book

You copied that incorrectly. It should look like this:

Function.prototype.method = function (name, func) {
    this.prototype[name] = func;
    return this;
};

 venueName = '<>&quot'; // for example

Entities should end with a ";". You forgot the one on quot.