Answers for "string operations in javascript"

is string javascript

function isString(value) {
	return typeof value === 'string' || value instanceof String;
}

isString(''); // true
isString(1); // false
isString({}); // false
isString([]); // false
isString(new String('teste')) // true

Strings in javascript

var abc = "abcdefghijklmnopqrstuvwxyz";
var esc = 'I don\'t \n know';   // \n new line
var len = abc.length;           // string length
abc.indexOf("lmno");            // find substring, -1 if doesn't contain 
abc.lastIndexOf("lmno");        // last occurance
abc.slice(3, 6);                // cuts out "def", negative values count from behind
abc.replace("abc","123");       // find and replace, takes regular expressions
abc.toUpperCase();              // convert to upper case
abc.toLowerCase();              // convert to lower case
abc.concat(" ", str2);          // abc + " " + str2
abc.charAt(2);                  // character at index: "c"
abc[2];                         // unsafe, abc[2] = "C" doesn't work
abc.charCodeAt(2);              // character code at index: "c" -> 99
abc.split(",");                 // splitting a string on commas gives an array
abc.split("");                  // splitting on characters
128.toString(16);               // number to hex(16), octal (8) or binary (2)

js string methods

// String methods:
'hello'.toUpperCase(); // "HELLO";
'LOL'.toLowerCase(); // "lol"
'    omg  '.trim(); // "omg"

// String methods with arguments:
// ==============================

//indexOf returns the index where the character is found (or -1 if not found)
'spider'.indexOf('i'); //2
'vesuvius'.indexOf('u'); //3 - only returns FIRST matching index
'cactus'.indexOf('z'); //-1 not found

// slice - returns a "slice" of a string
"pancake".slice(3); //"cake" - slice from index 3 onwards
"pancake".slice(0, 3); //"pan" - slice from index 0 up to index 3

// replace - returns a new string, with the FIRST match replaced
"pump".replace("p", "b"); //"bump" - only replaces first "p"

// String Template Literals
// Use backtick characters, NOT SINGLE QUOTES!

js strings

// Making Strings
let color = "purple";

// Single quotes work too:
let city = 'Tokyo';

//Strings have a length:
city.length; //5

//We can access specific characters using their index:
city[0]; //'T'
city[3]; //'y'

// String methods:
'hello'.toUpperCase(); // "HELLO";
'LOL'.toLowerCase(); // "lol"
'    omg  '.trim(); // "omg"

// String methods with arguments:
// ==============================

//indexOf returns the index where the character is found (or -1 if not found)
'spider'.indexOf('i'); //2
'vesuvius'.indexOf('u'); //3 - only returns FIRST matching index
'cactus'.indexOf('z'); //-1 not found

// slice - returns a "slice" of a string
"pancake".slice(3); //"cake" - slice from index 3 onwards
"pancake".slice(0, 3); //"pan" - slice from index 0 up to index 3

// replace - returns a new string, with the FIRST match replaced
"pump".replace("p", "b"); //"bump" - only replaces first "p"

// String Template Literals
// Use backtick characters, NOT SINGLE QUOTES!
// ========================
const color = "olive green";
const msg = `My favorite color is: ${color}` //"My favorite color is: olive green"

const str = `There are ${60 * 60 * 24} seconds in a day`//"There are 86400 seconds in a day"

javascript string

const string1 = "A string primitive";
const string2 = 'Also a string primitive';
const string3 = `Yet another string primitive`;