DEV Community

Cover image for Essential Vanilla JavaScript Functions
Amit Merchant
Amit Merchant

Posted on

Essential Vanilla JavaScript Functions

#javascript #procedural #functions #programming

Essential Vanilla JavaScript Functions

Some of the missing functions in JavaScript in vanilla form (inspired by PHP). You can just try it as a programming practice.

Array Functions

array_unique()

Remove duplicates from an array

function array_unique(arr){
    var seen = {};
    var ret_arr = [];
    var key;
    var i;

    function keyify(obj){
        var ret = "";
        var j;

        if (Object.prototype.toString.call(obj) === "[object Object]" || Object.prototype.toString.call(obj) === "[object Array]"){
            for (j in obj){
                ret += "~" + j + "^" + keyify(obj[j]) + "%";
            }
            return ret;
        }else{
          return obj;
        }
    }

    for(i = 0; i < arr.length; i++){
        key = keyify(arr[i]);
        if(!(key in seen)){
            ret_arr.push(arr[i]);
            seen[key] = true;
        }
    }

    return ret_arr;
}

array_unique([4,5,4,6,7,8,2,6]);
// [4, 5, 6, 7, 8, 2]
array_unique([{a: 'val'}, {b: 'val', c: 'val'}, 'a', 'b', [1,2,3,4], {a: 'val'}, [1,2,3,4], [{a: 'val'}, {b: 'val'}], [{a: 'val'}, {b: 'val'}]]);
// [{a: 'val'}, {b: 'val', c: 'val'}, 'a', 'b', [1,2,3,4], [{a: 'val'}, {b: 'val'}]]
Enter fullscreen mode Exit fullscreen mode

array_merge()

Merge two arrays

function array_merge(arr1, arr2){
    for(var i=0; i<arr2.length; i++){
        arr1.push(arr2[i]);
    }

    return arr1;
}

array_merge([1, 2, 3], [4, 5]);
// [1, 2, 3, 4, 5]
Enter fullscreen mode Exit fullscreen mode

array_chunk()

Splits an array into chunks of arrays

function array_chunk(arr, count){
    var temp_arr = [];

    for(var i=0; i<arr.length;){
        var chunk_arr = [];
        for(var j=0; j<count; j++){
            if(!arr[i])
                break;
            chunk_arr.push(arr[i]);
            i++;
        }
        temp_arr.push(chunk_arr);
    }

    return temp_arr;
}

array_chunk([1,2,3,4,5,6,7,8,9], 4);
// [ [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ], [ 9 ] ]
Enter fullscreen mode Exit fullscreen mode

array_collapse()

Collapses a collection of arrays into a single, flat array


function array_collapse(...arrays){
    var collapse_arr = [];

    for(var i=0; i<arrays.length;i++){
        for(var j=0; j<arrays[i].length; j++){
            collapse_arr.push(arrays[i][j]);
        }
    }

    return collapse_arr;
}

array_collapse([1, 2, 3, 4], [5, 6], ["hello", "world"]);
// [ 1, 2, 3, 4, 5, 6, 'hello', 'world' ]
Enter fullscreen mode Exit fullscreen mode

array_diff()

Returns the values in the arr1 that are not present in arr2

function array_diff(arr1, arr2){
    var temp_arr = [];

    for(var i=0; i<arr1.length; i++){
        if(arr2.indexOf(arr1[i]) == -1){  
            temp_arr.push(arr1[i]);
        }
    }

    return temp_arr;
}

array_diff([4,5,6,7, "unicorn"], [5, 6, 7]);
// [ 4, 'unicorn' ]
Enter fullscreen mode Exit fullscreen mode

array_intersect()

Returns the values common in the two supplied arrays

function array_intersect(arr1, arr2){
    var temp_arr = [];

    for(var i=0; i<arr1.length; i++){
        if(arr2.indexOf(arr1[i]) != -1){  
            temp_arr.push(arr1[i]);
        }
    }

    return temp_arr;
}

array_intersect([4,5,6,7, "unicorn"], [5, 6, 7, 8]);
// [ 5, 6, 7 ]
Enter fullscreen mode Exit fullscreen mode

array_map()

Sends each value of an array to a user-made function, which returns new values

function array_map(arr, func){
    var temp_arr = [];

    if(typeof func !== "function")
        throw "Second parameter should be a function";

    for(var i=0; i<arr.length; i++){
        temp_arr.push(func(arr[i]));
    }

    return temp_arr;
}

array_map([1, 2, 3, 4, 5], function (value) {
    return value * 2;
});
// [ 2, 4, 6, 8, 10 ]
Enter fullscreen mode Exit fullscreen mode

array_reject()

Filters the array using the given callback. The callback should return true if the item should be removed from the resulting array

function array_reject(arr, func){
    var temp_arr = [];

    if(typeof func !== "function")
        throw "Second parameter should be a function";

    for(var i=0; i<arr.length; i++){
        if(func(arr[i]))
            temp_arr.push(arr[i]);
    }

    return temp_arr;
}

array_reject([1, 2, 3, 4, 5], function (value) {
    return value > 3;
});
// [ 4, 5 ]
Enter fullscreen mode Exit fullscreen mode

array_split()

Breaks an array into the given number of groups

function array_split(arr, count){
    var temp_arr = [];
    var arr_length = arr.length;

    var chunk = Math.floor(arr_length/count);

    for(var i=0; i<arr.length;){
        var chunk_arr = [];

        if(temp_arr.length == (count-1))
            chunk = chunk + (arr_length-i);

        for(var j=0; j<chunk; j++){
            if(!arr[i])
                break;
            chunk_arr.push(arr[i]);
            i++;
        }

        temp_arr.push(chunk_arr);
    }

    return temp_arr;
}

array_split([1,2,3,4,5,6,7,8,9], 4);
// [ [ 1, 2 ], [ 3, 4 ], [ 5, 6 ], [ 7, 8, 9 ] ]
Enter fullscreen mode Exit fullscreen mode

array_take()

Returns a new array with the specified number of items

function array_take(arr, count){
    var temp_arr = [];

    if(count<0){
        count = Math.abs(count);
        for(var i=(arr.length-count); i<arr.length; i++){
            temp_arr.push(arr[i]);
        }
    }else{
        for(var i=0; i<count; i++){
            temp_arr.push(arr[i]);
        }
    }

    return temp_arr;
}

array_take([1,2,3,4,5,6,7,8,9], 4);
// [ 1, 2, 3, 4 ]
Enter fullscreen mode Exit fullscreen mode

You may also pass a negative integer to take the specified amount of items from the end of the array:

array_take([1,2,3,4,5,6,7,8,9], -3);
// [ 7, 8, 9 ]
Enter fullscreen mode Exit fullscreen mode

array_pad()

Inserts a specified number of items, with a specified value, to an array


function array_pad(arr, size, value){
    for(var i=0; i<size; i++){
        arr.push(value);
    }
    return arr;
}

array_pad([1,2,3,4], 2, "unicorn");
// [ 1, 2, 3, 4, 'unicorn', 'unicorn' ]
Enter fullscreen mode Exit fullscreen mode

range()

Creates an array containing a range of elements

function range(start, end){
    var temp_arr = [];

    for(var i=start; i<=end; i++){
        temp_arr.push(i);
    }

    return temp_arr;
}

range(5, 11);
// [ 5, 6, 7, 8, 9, 10, 11 ]
Enter fullscreen mode Exit fullscreen mode

String Functions

chunk_split()

Splits a string into a series of smaller parts

function chunk_split(string, length, end){
    var temp_string = '';

    for(var i=0; i<string.length; i++){
        temp_string += string[i];
        if((i+1)%length==0)
            temp_string += end;
    }

    return temp_string;
}

console.log(chunk_split("Hello", 1 , "."));
// H.e.l.l.o.
console.log(chunk_split("Hello", 1 , ".."));
// H..e..l..l..o..
Enter fullscreen mode Exit fullscreen mode

str_pad()

Pads a string to a new length

function str_pad(string, size, value){
    for(var i=0; i<size; i++){
        string += value;
    }

    return string;
}

str_pad("unicorn", 5 , ".");
// unicorn.....
Enter fullscreen mode Exit fullscreen mode

strrev()

Reverses a string

function strrev(string){
    var temp_string = '';

    for(var i=string.length-1; i>=0; i--){
        temp_string += string[i];
    }

    return temp_string;
}

strrev("unicorn");
// nrocinu
Enter fullscreen mode Exit fullscreen mode

similar_text()

Calculates the similarity between two strings

function similar_text(string1, string2){
    var seen = {};
    var similar_count = 0;

    for(var i=0; i<string1.length; i++){
        if((string2.indexOf(string1[i]) !== -1 && !(string1[i] in seen)) 
                || string1[i]==' ')
        {
            similar_count++;
            if(string1[i]!='')
                seen[string1[i]] = true;
        }
    }

    return similar_count;
}

similar_text("Hello World","Hello Peter");
// 6
Enter fullscreen mode Exit fullscreen mode

Originally published at amitmerchant1990/essential-vanilla-javascript-functions.

Top comments (13)

Collapse
 
lexlohr profile image
Alex Lohr •

Interesting approach for array_unique (even taking into account that objects and arrays in the array might have different pointers, but have the same content. There's just one minor issue: x in y will also return true for the constructor attribute, so better use y.hasOwnProperty(x). If your array contains 'constructor' as a string, your function will filter it out.

Collapse
 
amit_merchant profile image
Amit Merchant •

Yeah. We can implement it that way as well. If you want you can send over a pull request on github.com/amitmerchant1990/essent...

Collapse
 
lexlohr profile image
Alex Lohr •

There you go.

Collapse
 
rehia profile image
Jérôme Avoustin •

Sorry, but while the big majority of these functions are pretty useless (you might find them in lodash or even in the language itself), the implementations show a big misunderstanding of how JavaScript works.
You can do pretty much anything with Array functions like map, reduce, filter, slice and concat. They are helpful because they do not mutate the original array, but produce a new one.
And finally, it is really not necessary to pollute your code with such ugly names, even if PHP provides them. Next readers won't necessary know a lot about PHP.

Collapse
 
eerk profile image
eerk •

This, and you can even use the ...spread operator instead of concat, to create a new array from an existing one.
The above functions are translated a bit too literally from PHP, or perhaps the intention was to make them work for ES5 / lower?

Collapse
 
hoffmann profile image
Peter Hoffmann •

Why are map, reject and taken part of your list (they already exist in vanilla JS)? When (besides an job interview) did you have the need for strrev?
Besides that a very nice exercise.

Collapse
 
amit_merchant profile image
Amit Merchant • • Edited

Pardon me for that. I was curious and was just trying to do my implementation.

Collapse
 
weswedding profile image
Weston Wedding •

Gotta give a shout out to Locutus here, a source for hundreds of Javascript implementations of PHP functions (and other languages).

Collapse
 
tobbwiz profile image
Bernard Sibanda •

I love what you have done. Keep it up. The raised point on mutation is a good one. These need to process cloned objects not original. With regard these (map, reduce, filter, slice and concat), blind use of these is as good as blind use of frameworks.

Collapse
 
meisekimiu profile image
Natalie Martin •

Neat! I love doing things in Vanilla JavaScript over including a big library whenever I can. However, to make the code a bit nicer I'd suggest adding the array and string methods to their actual object prototypes if possible. In my opinion it makes the code look much nicer and is a convenience Javascript has the original PHP functions do not. (That's the reason PHP has so many functions that start with "array" or "string")

Collapse
 
gcdcoder profile image
Gustavo Castillo • • Edited

Awesome utilities, just one question, what is this line for?

ret += "~" + j + "^" + keyify(obj[j]) + "%";

Why do you use "~", ^ and "%"?

Collapse
 
gregorgonzalez profile image
Gregor Gonzalez •

Yes! This is exactly what I needed. As a PHP developer I always use those functions. Thank you.

Collapse
 
ryanhaber profile image
Ryan Haber •

Fun. Thanks!

View full discussion (13 comments)

Read next

mikeyoung44 profile image

Undetectable Backdoors in Outsourced Machine Learning Models: A Theoretical Vulnerability

Mike Young -

mdarifulhaque profile image

2563. Count the Number of Fair Pairs

MD ARIFUL HAQUE -

razaulhaque1334 profile image

Software knowledge

Md. Razaul Haque -

gladiatorsbattle profile image

Building a Highly Reactive Page in React: A Deep Dive into Gladiator Crash

Gladiators Battle -