join

Arrays topic in TypeScript is divided into following parts:

Below are the methods that are discussed in this section

concat	every	filter
forEach	indexOf	join

concat

This contacts two or more arrays and returns a new array.
Syntax

array1.concat(array2, array3,...);

Below is a sample code

var nums:string[] = new Array("10","20","30");
var chars:string[] = new Array('a','b','c');
var strings:string[] = new Array("Hello","Hi");
var i:number;
var newArray = strings.concat(chars, nums);
for(i=0; i<newArray.length; i++){
    console.log(newArray[i]);
}

Below is the output of above code

every

This method tests whether all array elements passes the test implemented by the function.
– Returns true is all the array elements passes in the function test, otherwise false.
– functionName is the name of the function used to test the array elements
Syntax

arrayName.every(functionName);

Below is a sample code

// returns true
function test1(element, index, array) { 
    return (element >= 10); 
 } 
 var nums1:number[] = [10,20,30];
 var result1 = nums1.every(test1); 
 console.log("Test Value : " + result1);

 // returns false
 function test2(element, index, array) { 
    return (element > 10); 
 } 
 var nums2:number[] = [10,5,30];
 var result2 = nums2.every(test2); 
 console.log("Test Value : " + result2 );

Below is the output of above code

filter

This function will create a new array with the elements that passes a test implemented by a function.
– Returns a new array
– functionName is the name of the function used to test the array elements
Syntax

arrayName.filter(functionName);

Below is a sample code

function even(element, index, array) { 
    return (element%2 == 0); 
 } 
 var nums1:number[] = [5,10,20,30,105,64];
 var result1 = nums1.filter(even); 
 console.log("Even Numbers: " + result1);

Below is the output of above code

forEach

This method calls a function for each element in the array.
Syntax

arrayName.forEach(funcionName)

Below is an example

let users = ["Akanksha","Aarav","Anita","Raj"];
users.forEach(function(value){
    console.log(value);
});

Below is the output of above code

indexOf

This method will return the first index in which the element is found. It will return -1 if the element is not found.
– Returns the first index in which the element is found. It only returns one index even if the value is present at multiple indexes
– value: the value which we are looking in the array
– fromIndex: the index from which we want to start the search. This is optional. By default, it will start the search from the beginning of the array.
Syntax

arrayName.indexOf(value, [fromIndex[);

Below is an example

var nums:number[] = [10,20,30,20,40,50,10];
console.log("Original array: " + nums);
console.log("Search for value 20: " + nums.indexOf(20));
console.log("Search for value 20, search start from 2nd index: " + nums.indexOf(20,2));
console.log("Search for 50: " + nums.indexOf(50));

Below is the output of above code

This method joins all the array elements into a string. We can pass a custom separator which can be used to separate the array values in the string. By default, it will use comma (,) as a separator.
Syntax

arrayName.join(separator);

Below is an example

var users:string[] = ["Akanksha","Aarav","Apoorv","Anita","Raj"];
console.log("Original Array: " + users);
console.log(users.join());
console.log(users.join(", "));
console.log(users.join(" "));
console.log(users.join("# "));

Below is the output of above code

Tag: join

Methods in Arrays – Part 1

concat

every

filter

forEach

indexOf

join