Thursday, May 20, 2021

Javascript Practice 56: JS Hero - Array: indexOf()

 
Question: 

Write a function add that adds an element to the end of an array. However, the element should only be added if it is not already in the array.

Example: add([1, 2], 3) should return [1, 2, 3] and add([1, 2], 2) should return [1, 2].




Answer: 

function add (arr, e) {

if (arr.indexOf(e) === -1) {

arr.push(e);
return arr;

} else {

return arr; 

}
}; 





> declare a function add
> it has 2 parameters arr & e
> we need to first check if 'e' is already present in the array - arr
> if it is present then it will not be added to the array - arr 
> if it is not present then it will be added to the array - arr
> so after we declare the function, we will open an if / else statement
> the condition will be to check if the indexOf method on the array contains the 'e' element
> if it returns the -1 or is equal to -1, then we shall add that element using the push method
> or else we shall just return the original array 

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