Best solutions in JavaScript – part 1

good2

Level: intermediate

Update 09-2014 : note – this article has been originally created several years ago, so maybe a little different from today’s standards of good and recommended solutions.

Today we recommend the first part of best practices and solutions in JavaScript. It is purely practical. We present tips and simple tricks.

Best solutions in JavaScript

An example for a good start – adding a dynamic element to the document (use of DOM):

<div id="some_div">In this element we will add the next...</div>
// dom_create_input.js
function createInput() {
    var input = document.createElement("input");
    input.name = "user_location"; // field name
    input.id = "user_location"; // id
    input.value = ""; // default value
    input.style.width = "150px"; // CSS options

    // readonly, or other options ...

    document.getElementById("some_div").appendChild(input);
}

And that’s all.

Another trick is to send the form by clicking the link.

Example – send the form through plain link:

<a href="javascript:document.forms[0].submit()">OK</a>

How quickly set a CSS class for the element in pure JavaScript?

Here is an example:

var cn = "foobar";
document.getElementById("elem_id").className = cn;

Thus, we already set CSS class “foobar” for the element.

OK, and how to obtain the text content from an HTML element using DOM operations?

Example – getting text values from elements such as div, h1, etc:

<h1 id="topic"> Test </h1>
var dTopic = document.getElementById('topic').firstChild.nodeValue;
alert(dTopic);

Let’s move on. How to write the simplest equivalent for the isset() function in JS?

Example:

function isset(variable) {
    if  (variable == undefined) {
        return false;
    }

    return true;
}

And here we have something better. It’s an implementation of isArray function. It’s a strict check whether the given argument is an array.

Example – checking whether the argument is an array in JavaScript:

// is_array JavaScript
var isArray = function(value) {
    return value && typeof value === 'object' &&
    typeof value.length === 'number' &&
    typeof value.splice === 'function' &&
    !(value.propertyIsEnumerable('length'));
};

// examples of use:
isArray('x'); // false
isArray(1); // false
isArray(new Array()); // true

And now, one of those simple tricks that I really like. It’s a concise and fast way to circumvent errors, such as when we don’t know if an item exists.

Such code tries to get the value of an item (in this case from an array), and returns either the value or the default value, which has been defined after OR logical operator (||).

Example:

var tab = new Array(); // ...
var myvar = tab["some_name"] || "(none)";
alert(myvar);

It just works, giving an elegant result, even if an element of the array (or object) doesn’t exist, and we’re trying to get a value from this element.


A little math, and regular expressions

By the way, I want to mention here about sharing of solutions. So if you know more best solutions and practices, tips and tricks, would be nice if you could post them as a comment below this article.

OK, let’s back to the code.

Example – factorial in JavaScript :

// factorial - JS
var factorial = function factorial(i, a) {
    a = a || 1;
    if (i < 2) {
        return a;
    }

    return factorial(i - 1, a * i);
};

alert(factorial(4)); // 24

Yes, we love maths.

OK, now we remind an example shown already when discussing regular expressions:

Example – parsing URLs:

var parse_url = /^(?:([A-Za-z]+):)?(\/{0,3})([0-9.\-A-Za-z]+)(?::(\d+))?(?:\/([^?#]*))?(?:\?([^#]*))?(?:#(.*))?$/;
 
var url = "http://www.server.com:80/stuff?q#fragment";
var result = parse_url.exec(url);
var names = ['url', 'protocol', 'slash', 'server', 'port',
    'path', 'query', 'anchor'];
 
var blanks = '              ';
var i;
for (i = 0; i < names.length; i += 1) {
    document.writeln(names[i] + ':' + blanks.substring(
        names[i].length), result[i]);
}

Below we have an interesting and practical example about using regular expressions to format fractions as real numbers.

Example – format fractions as real numbers in JavaScript:

function fractions(txt) {
    txt = txt.replace(/^ */, "");
    txt = txt.replace(/ *$/, "");
    txt = txt.replace(/(([0-9]+) *\/ *([0-9]+)).*/, "($2/$3)");
    txt = txt.replace(/ /, "+");
    
    return(eval(txt));
}

// examples of use
alert(fractions("1/4"));         // 0.25
alert(fractions(" 1 / 4 "));     // 0.25
alert(fractions(" 10 /80 "));    // 0.125
alert(fractions("2 3/8"));       // 2.375
alert(fractions("1 2/5 cala"));  // 1.4

The next example is a simulation of “varargs”, ie. variable list of function arguments, certainly well-known by programmers of languages ​​such as C.

Example – variable list of arguments in JavaScript:

// va_args JS
var sum = function() {
    var i, sum = 0;
    for (i = 0; i < arguments.length; i += 1) {
        sum += arguments[i];
    }
    
    return sum;
};

alert(sum(4, 8, 15, 16, 23, 42));  // 108

The numbers (variables of type Number) in JavaScript have native toString() method, which converts it to a string.

Example – toString for numbers (convert number to string in JavaScript):

var number = 5;
alert(typeof number); // number
number = number.toString(); // "5"
alert(typeof number); // string

// overriding the method (modified action)
Number.prototype.toString = function() {
    return String(this + 1);
};

var nv = number.toString();
alert(nv); // "6"

The code contains also an example of overriding the built-in method. In this case the number is increased by 1, and then converted to the String type.

And the last example for today – natural sorting in JavaScript.

Example – natural sort:

var m = ['aa', 'bb', 'a', 8, 4, 16, 15, 23, 42];
m.sort(function(a, b) {
    if (a === b) {
        return 0;
    }

    if (typeof a  === typeof b) {
        return a < b ? -1 : 1;
    }

    return typeof a < typeof b ? -1 : 1;
});

// m is now: [4, 8, 15, 16, 23, 42, 'a', 'aa', 'bb']
alert(m.toString());

Summary

And here we finish the first part of the series: Best solutions in JavaScript. Some of them were used to fix the problems encountered in real projects.

If any solution will be useful for at least one reader, I think the today’s job is done.

Thank you for your attention.

Web and Mobile Software Developer, with years of experience. My biggest passions are programming, new technologies, e-commerce, as well sports, cars, and of course my family.

Facebook Twitter LinkedIn Google+ Skype Xing 

Share: Share on Facebook1Tweet about this on TwitterShare on Google+0Share on LinkedIn1Share on Tumblr0Digg thisEmail this to someonePin on Pinterest1
Both comments and pings are currently closed.