如何从数组中删除除 javascript 中第一个元素之外的所有元素

Question

I want to remove all element from array except the element of array at 0th index

["a", "b", "c", "d", "e", "f"]

Output should be a

Answer 1

You can set the length property of the array.

 var input = ['a','b','c','d','e','f']; input.length = 1; console.log(input);

OR, Use splice(startIndex) method

 var input = ['a','b','c','d','e','f']; input.splice(1); console.log(input);

OR use Array.slice method

 var input = ['a','b','c','d','e','f']; var output = input.slice(0, 1) // 0-startIndex, 1 - endIndex console.log(output);

Answer 2

This is the head function. tail is also demonstrated as a complimentary function.

Note, you should only use head and tail on arrays that have a known length of 1 or more.

 // head :: [a] -> a const head = ([x,...xs]) => x; // tail :: [a] -> [a] const tail = ([x,...xs]) => xs; let input = ['a','b','c','d','e','f']; console.log(head(input)); // => 'a' console.log(tail(input)); // => ['b','c','d','e','f']

Answer 3

array = [a,b,c,d,e,f];
remaining = array[0];
array = [remaining];

Answer 4

You can use splice to achieve this.

Input.splice(0, 1);

More details here . . . http://www.w3schools.com/jsref/jsref_splice.asp

Answer 5

You can use slice:

 var input =['a','b','c','d','e','f']; input = input.slice(0,1); console.log(input);

Documentation: https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Array/slice

Answer 6

If you want to keep it in an array , you can use slice or splice . Or wrap the wirst entry again.

 var Input = ["a","b","c","d","e","f"]; console.log( [Input[0]] ); console.log( Input.slice(0, 1) ); console.log( Input.splice(0, 1) );

Answer 7

The shift() method is a perfect choice to do this.

var input = ['a','b','c','d','e','f'];  
let firstValue = input.shift();
console.log(firstValue);

Answer 8

var input = ["a", "b", "c", "d", "e", "f"];

[input[0]];

// ["a"]

Answer 9

var output=Input[0]

It prints the first element in case of you want to filter under some constrains

var Input = [ a, b, c, d, e, a, c, b, e ];
$( "div" ).text( Input.join( ", " ) );

Input = jQuery.grep(Input, function( n, i ) {
  return ( n !== c );
});