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4 Ways to Combine Strings in JavaScript

samanthaming profile image Samantha Ming Originally published at samanthaming.com ・5 min read

Code snippets of the 4 ways to combine strings using template strings, join, concat, and plus operator

Here are 4 ways to combine strings in JavaScript. My favorite way is using Template Strings. Why? Because it’s more readable, no backslash to escape quotes, no awkward empty space separator, and no more messy plus operators πŸ‘

const icon = 'πŸ‘‹';

// Template Strings
`hi ${icon}`;

// join() Method
['hi', icon].join(' ');

// Concat() Method
''.concat('hi ', icon);

// + Operator
'hi ' + icon;

// RESULT
// hi πŸ‘‹

1. Template Strings

If you come from another language, such as Ruby, you will be familiar with the term string interpolation. That's exactly what template strings is trying to achieve. It's a simple way to include expressions in your string creation which is readable and concise.

const name = 'samantha';
const country = 'πŸ‡¨πŸ‡¦';

Problem of Missing space in String concatenation

Before template strings, this would be the result of my string 😫

"Hi, I'm " + name + "and I'm from " + country;

☝️ Did you catch my mistake? I'm missing a space 😫. And that's a super common issue when concatenating strings.

// Hi, I'm samanthaand I'm from πŸ‡¨πŸ‡¦

Resolved with Template Strings

With template strings, this is resolved. You write exactly how you want your string to appear. So it's very easy to spot if a space is missing. Super readable now, yay! πŸ‘

`Hi, I'm ${name} and I'm from ${country}`;

2. join()

The join method combines the elements of an array and returns a string. Because it's working with array, it's very handy if you want to add additional strings.

const array = ['My handles are'];
const handles = [instagram, twitter, tiktok].join(', '); // @samanthaming, @samantha_ming, @samanthaming

array.push(handles); // ['My handles are', '@samanthaming, @samantha_ming, @samanthaming']

array.join(' '); 

// My handles are @samanthaming, @samantha_ming, @samanthaming

Customize Separator

The great thing about join is that you can customize how your array elements get combined. You can do this by passing a separator in its parameter.

const array = ['My handles are '];
const handles = [instagram, twitter, tiktok].join(', '); // @samanthaming, @samantha_ming, @samanthaming

array.push(handles);

array.join('');

// My handles are @samanthaming, @samantha_ming, @samanthaming

3. concat()

With concat, you can create a new string by calling the method on a string.

const instagram = '@samanthaming';
const twitter = '@samantha_ming';
const tiktok = '@samanthaming';

'My handles are '.concat(instagram, ', ', twitter', ', tiktok);

// My handles are @samanthaming, @samantha_ming, @samanthaming

Combining String with Array

You can also use concat to combine a string with an array. When I pass an array argument, it will automatically convert the array items into a string separated by a comma ,.

const array = [instagram, twitter, tiktok];

'My handles are '.concat(array);

// My handles are @samanthaming,@samantha_ming,@samanthaming

If you want it formatted better, we can use join to customize our separator.

const array = [instagram, twitter, tiktok].join(', ');

'My handles are '.concat(array);
// My handles are @samanthaming, @samantha_ming, @samanthaming

4. Plus Operator (+)

One interesting thing about using the + operator when combining strings. You can use to create a new string or you can mutate an existing string by appending to it.

Non-Mutative

Here we are using + to create a brand new string.

const instagram = '@samanthaming';
const twitter = '@samantha_ming';
const tiktok = '@samanthaming';

const newString = 'My handles are ' + instagram + twitter + tiktok;

Mutative

We can also append it to an existing string using +=. So if for some reason, you need a mutative approach, this might be an option for you.

let string = 'My handles are ';

string += instagram + twitter;

// My handles are @samanthaming@samantha_ming

OH darn 😱 Forgot the space again. SEE! It's so easy to miss a space when concatenating strings.

string += instagram + ', ' + twitter + ', ' + tiktok;

// My handles are @samanthaming, @samantha_ming, @samanthaming

That feels so messy still, let's throw join in there!

string += [instagram, twitter, tiktok].join(', ');

// My handles are @samanthaming, @samantha_ming, @samanthaming

Escaping Characters in Strings

When you have special characters in your string, you will need to first escape these characters when combining. Let's look through a few scenarios and see how we can escape them πŸ’ͺ

Escape Single Quotes or Apostrophes (')

When creating a string you can use single or double quotes. Knowing this knowledge, when you have a single quote in your string, a very simple solution is to use the opposite to create the string.

const happy = πŸ™‚;

["I'm ", happy].join(' ');

''.concat("I'm ", happy);

"I'm " + happy;

// RESULT
// I'm πŸ™‚

Of course, you can also use the backslash, \ , to escape characters. But I find it a bit difficult to read, so I don't often do it this way.

const happy = πŸ™‚;

['I\'m ', happy].join(' ');

''.concat('I\'m ', happy);

'I\'m ' + happy;

// RESULT
// I'm πŸ™‚

Because Template strings is using backtick, this scenario doesn't apply to it πŸ‘

Escape Double Quotes (")

Similar to escaping single quotes, we can use the same technique of using the opposite. So for escaping double quotes, we will use single quotes.

const flag = 'πŸ‡¨πŸ‡¦';

['Canada "', flag, '"'].join(' ');

''.concat('Canada "', flag, '"');

'Canada "' + flag + '"';

// RESULT
// Canada "πŸ‡¨πŸ‡¦"

And yes, can also use the backslash escape character.

const flag = 'πŸ‡¨πŸ‡¦';

['Canada "', flag, '"'].join(' ');

''.concat('Canada "', flag, '"');

'Canada "' + flag + '"';

// RESULT
// Canada "πŸ‡¨πŸ‡¦"

Because Template strings is using backtick, this scenario doesn't apply to it πŸ‘

Escape backtick

Because Template strings is using backticks to create its string, when do want to output that character, we have to escape it using backslash.

const flag = 'πŸ‡¨πŸ‡¦';

`Use backtick \`\` to create a template string`;

// RESULT
// Use backtick `` to create a template string

Because the other string creations are not using backtick, this scenario doesn't apply to them πŸ‘

Which way to use?

I showed a few examples of using the different ways of concatenating strings. Which way is better all depends on the situation. When it comes to stylistic preference, I like to follow Airbnb Style guide.

When programmatically building up strings, use template strings instead of concatenation. eslint: prefer-template template-curly-spacing

So template strings for the win! πŸ‘‘

Why the other ways still matter?

It's still important to know the other ways as well. Why? Because not every code base will follow this rule or you might be dealing with a legacy code base. As a developer, we need to be able to adapt and understand whatever environment we're thrown in. We're there to problem solve not complain how old the tech is lol πŸ˜‚ Unless that complaining is paired with tangible action to improve. Then we got progress πŸ‘

Browser Support

Browser Template String join concat +
Internet Explorer ❌ βœ… IE 5.5 βœ… IE 4 βœ… IE 3
Edge βœ… βœ… βœ… βœ…
Chrome βœ… βœ… βœ… βœ…
Firefox βœ… βœ… βœ… βœ…
Safari βœ… βœ… βœ… βœ…

Resources


Thanks for reading ❀
To find more code tidbits, please visit samanthaming.com

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Discussion

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functional_js profile image
Functional Javascript

Great work Samantha.

Performance Test


const icon = 'πŸ‘‹';

timeInLoop("template literal", 1e6, () => `hi ${icon}`);

timeInLoop("plus operator", 1e6, () => "hi " + icon);

timeInLoop("concat func", 1e6, () => ''.concat('hi ', icon));

timeInLoop("arr join", 1e6, () => ['hi', icon].join(' '));

/*
@perftests
run 1 million times each

template literal: 1e+6:     14.575ms
plus operator:    1e+6:     53.776ms
concat func:      1e+6:     391.723ms
arr join:         1e+6:     681.97ms

*/

Source Code for timeInLoop func

gist.github.com/funfunction/91b587...

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Samantha Ming Author

Great! thanks for the performance test πŸ‘

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psanchez1982 profile image
Patricio Sanchez Alvial

In most language they tried to avoid using the + operator because created a new string between each plus and affected performance

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samanthaming profile image
Samantha Ming Author

OH! Didn't know that, thanks for sharing! I'll have to add it to my notes πŸ‘

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mohsenalyafei profile image
Mohsen Alyafei

Which one is more efficient on large strings?