JavaScript Basic Info and String Concatenation


Strings in JavaScript can be enclosed in Single quotes 'hello', Double quotes "Hello" and (from ES2015, ES6) in Template Literals (backticks) `hello`.

var hello  = "Hello";
var world  = 'world';
var helloW = `Hello World`;              // ES2015 / ES6

Strings can be created from other types using the String() function.

var intString = String(32); // "32"
var booleanString = String(true); // "true"
var nullString = String(null); // "null" 

Or, toString() can be used to convert Numbers, Booleans or Objects to Strings.

var intString = (5232).toString(); // "5232"
var booleanString = (false).toString(); // "false"
var objString = ({}).toString(); // "[object Object]"

Strings also can be created by using String.fromCharCode method.

String.fromCharCode(104,101,108,108,111) //"hello"

Creating a String object using new keyword is allowed, but is not recommended as it behaves like Objects unlike primitive strings.

var objectString = new String("Yes, I am a String object");
typeof objectString;//"object"
typeof objectString.valueOf();//"string"

Concatenating Strings

String concatenation can be done with the + concatenation operator, or with the built-in concat() method on the String object prototype.

var foo = "Foo";
var bar = "Bar";
console.log(foo + bar);        // => "FooBar"
console.log(foo + " " + bar);  // => "Foo Bar"

foo.concat(bar)            // => "FooBar"
"a".concat("b", " ", "d")  // => "ab d"

Strings can be concatenated with non-string variables but will type-convert the non-string variables into strings.

var string = "string";
var number = 32;
var boolean = true;

console.log(string + number + boolean); // "string32true"

String Templates


Strings can be created using template literals (backticks) `hello`.

var greeting = `Hello`;

With template literals, you can do string interpolation using ${variable} inside template literals:

var place = `World`;
var greet = `Hello ${place}!`

console.log(greet); // "Hello World!"

You can use String.raw to get backslashes to be in the string without modification.

`a\\b` // =  a\b
String.raw`a\\b` // = a\\b