Is it advisable to alter the prototype of String in JavaScript?

Question

Is it advisable to alter the prototype of String in JavaScript?

As I was in the process of creating a trim function in JavaScript, I decided to do some research before reinventing the wheel. After a quick Google search, I stumbled upon this helpful link:

The solution provided on the website is as follows:

String.prototype.trim = function() {
    return this.replace(/^\s+|\s+$/g,"");
}
String.prototype.ltrim = function() {
    return this.replace(/^\s+/,"");
}
String.prototype.rtrim = function() {
    return this.replace(/\s+$/,"");
}

Furthermore, it suggests an alternative method for those who prefer not to modify the prototype of String:

function trim(stringToTrim) {
    return stringToTrim.replace(/^\s+|\s+$/g,"");
}
function ltrim(stringToTrim) {
    return stringToTrim.replace(/^\s+/,"");
}
function rtrim(stringToTrim) {
    return stringToTrim.replace(/\s+$/,"");
}

I am curious about the scenarios where it is recommended not to modify the prototype of String or any object. Can you provide insight on this?

javascript prototype

Answer 1

Answer №1

The trim function will be standardized in ECMAScript Fifth Edition, and it is already available in some browsers. Therefore:

It is acceptable to add them to the prototype.
However, if the trim functions are already present, it is best not to add them to the prototype as it may replace a fast native-code function with a slower JavaScript one.

Typically, it is slightly faster to perform trim using two replace methods:

// Add ECMA262-5 string trim if not supported natively
//
if (!('trim' in String.prototype)) {
    String.prototype.trim= function() {
        return this.replace(/^\s+/, '').replace(/\s+$/, '');
    };
}

Answer 2

The trim function will be standardized in ECMAScript Fifth Edition, and it is already available in some browsers. Therefore:

It is acceptable to add them to the prototype.
However, if the trim functions are already present, it is best not to add them to the prototype as it may replace a fast native-code function with a slower JavaScript one.

Typically, it is slightly faster to perform trim using two replace methods:

// Add ECMA262-5 string trim if not supported natively
//
if (!('trim' in String.prototype)) {
    String.prototype.trim= function() {
        return this.replace(/^\s+/, '').replace(/\s+$/, '');
    };
}

Answer 3

Answer №2

As a general rule, it is best not to modify prototypes of built-in objects. However, you can definitely add your own useful functions.

Always remember to check before you make any additions:

//pre-1.6 javascript
if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(elt) {
        var len = this.length >>> 0;
        var from = Number(arguments[1]) || 0;
        from = (from < 0) ? Math.ceil(from) : Math.floor(from);
        if (from < 0)
            from += len;
        for (; from < len; from++) {
            if (from in this && this[from] === elt)
                return from;
        }
        return -1;
    };
}

By following this approach, you avoid overwriting potentially faster built-in functions that may be introduced in future updates.

Answer 4

As a general rule, it is best not to modify prototypes of built-in objects. However, you can definitely add your own useful functions.

Always remember to check before you make any additions:

//pre-1.6 javascript
if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(elt) {
        var len = this.length >>> 0;
        var from = Number(arguments[1]) || 0;
        from = (from < 0) ? Math.ceil(from) : Math.floor(from);
        if (from < 0)
            from += len;
        for (; from < len; from++) {
            if (from in this && this[from] === elt)
                return from;
        }
        return -1;
    };
}

By following this approach, you avoid overwriting potentially faster built-in functions that may be introduced in future updates.

Answer 5

Answer №3

If you're looking to enhance the functionality of this utility, consider adjusting the prototype. Keep in mind that the function might already be built into certain browsers, so it's worth checking here: https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Objects/String

Answer 6

If you're looking to enhance the functionality of this utility, consider adjusting the prototype. Keep in mind that the function might already be built into certain browsers, so it's worth checking here: https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Objects/String

Is it advisable to alter the prototype of String in JavaScript?

Answer №1

Answer №2

Answer №3

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