问题
Is there a way in JavaScript to compare values from one array and see if it is in another array?
Similar to PHP\'s in_array function?
回答1:
No, it doesn't have one. For this reason most popular libraries come with one in their utility packages. Check out jQuery's inArray and Prototype's Array.indexOf for examples.
jQuery's implementation of it is as simple as you might expect:
function inArray(needle, haystack) {
var length = haystack.length;
for(var i = 0; i < length; i++) {
if(haystack[i] == needle) return true;
}
return false;
}
If you are dealing with a sane amount of array elements the above will do the trick nicely.
EDIT: Whoops. I didn't even notice you wanted to see if an array was inside another. According to the PHP documentation this is the expected behavior of PHP's in_array:
$a = array(array('p', 'h'), array('p', 'r'), 'o');
if (in_array(array('p', 'h'), $a)) {
echo "'ph' was found\n";
}
if (in_array(array('f', 'i'), $a)) {
echo "'fi' was found\n";
}
if (in_array('o', $a)) {
echo "'o' was found\n";
}
// Output:
// 'ph' was found
// 'o' was found
The code posted by Chris and Alex does not follow this behavior. Alex's is the official version of Prototype's indexOf, and Chris's is more like PHP's array_intersect. This does what you want:
function arrayCompare(a1, a2) {
if (a1.length != a2.length) return false;
var length = a2.length;
for (var i = 0; i < length; i++) {
if (a1[i] !== a2[i]) return false;
}
return true;
}
function inArray(needle, haystack) {
var length = haystack.length;
for(var i = 0; i < length; i++) {
if(typeof haystack[i] == 'object') {
if(arrayCompare(haystack[i], needle)) return true;
} else {
if(haystack[i] == needle) return true;
}
}
return false;
}
And this my test of the above on it:
var a = [['p','h'],['p','r'],'o'];
if(inArray(['p','h'], a)) {
alert('ph was found');
}
if(inArray(['f','i'], a)) {
alert('fi was found');
}
if(inArray('o', a)) {
alert('o was found');
}
// Results:
// alerts 'ph' was found
// alerts 'o' was found
Note that I intentionally did not extend the Array prototype as it is generally a bad idea to do so.
回答2:
Array.indexOf was introduced in JavaScript 1.6, but it is not supported in older browsers. Thankfully the chaps over at Mozilla have done all the hard work for you, and provided you with this for compatibility:
if (!Array.prototype.indexOf)
{
Array.prototype.indexOf = function(elt /*, from*/)
{
var len = this.length >>> 0;
var from = Number(arguments[1]) || 0;
from = (from < 0)
? Math.ceil(from)
: Math.floor(from);
if (from < 0)
from += len;
for (; from < len; from++)
{
if (from in this &&
this[from] === elt)
return from;
}
return -1;
};
}
There are even some handy usage snippets for your scripting pleasure.
回答3:
There is now Array.prototype.includes:
The includes() method determines whether an array includes a certain element, returning true or false as appropriate.
var a = [1, 2, 3];
a.includes(2); // true
a.includes(4); // false
Syntax
arr.includes(searchElement)
arr.includes(searchElement, fromIndex)
回答4:
If the indexes are not in sequence, or if the indexes are not consecutive, the code in the other solutions listed here will break. A solution that would work somewhat better might be:
function in_array(needle, haystack) {
for(var i in haystack) {
if(haystack[i] == needle) return true;
}
return false;
}
And, as a bonus, here's the equivalent to PHP's array_search (for finding the key of the element in the array:
function array_search(needle, haystack) {
for(var i in haystack) {
if(haystack[i] == needle) return i;
}
return false;
}
回答5:
There is a project called Locutus, it implements PHP functions in Javascript and in_array() is included, you can use it exactly as you use in PHP.
Examples of use:
in_array('van', myArray);
in_array(1, otherArray, true); // Forcing strict type
回答6:
var a = [1,2,3,4,5,6,7,8,9];
var isSixInArray = a.filter(function(item){return item==6}).length ? true : false;
var isSixInArray = a.indexOf(6)>=0;
回答7:
jQuery solution is available, check the ducumentation here: http://api.jquery.com/jquery.inarray/
$.inArray( 10, [ 8, 9, 10, 11 ] );
回答8:
If you only want to check if a single value is in an array, then Paolo's code will do the job. If you want to check which values are common to both arrays, then you'll want something like this (using Paolo's inArray function):
function arrayIntersect(a, b) {
var intersection = [];
for(var i = 0; i < a.length; i++) {
if(inArray(b, a[i]))
intersection.push(a[i]);
}
return intersection;
}
This wil return an array of values that are in both a and b. (Mathematically, this is an intersection of the two arrays.)
EDIT: See Paolo's Edited Code for the solution to your problem. :)
回答9:
If you need all the PHP available parameters, use this:
function in_array(needle, haystack, argStrict) {
var key = '', strict = !!argStrict;
if (strict) {
for (key in haystack) {
if (haystack[key] === needle) {
return true;
}
}
}
else {
for (key in haystack) {
if (haystack[key] == needle) {
return true;
}
}
}
return false;
}
回答10:
Add this code to you project and use the object-style inArray methods
if (!Array.prototype.inArray) {
Array.prototype.inArray = function(element) {
return this.indexOf(element) > -1;
};
}
//How it work
var array = ["one", "two", "three"];
//Return true
array.inArray("one");
回答11:
There is an equivalent function:
includes()
Look here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes
回答12:
With Dojo Toolkit, you would use dojo.indexOf(). See dojo.indexOf for the documentation, and Arrays Made Easy by Bryan Forbes for some examples.
回答13:
haystack.find(value => value == needle)
where haystack is an array and needle is an element in array. If element not found will be returned undefined else the same element.
回答14:
function in_array(what, where) {
var a=false;
for (var i=0; i<where.length; i++) {
if(what == where[i]) {
a=true;
break;
}
}
return a;
}
回答15:
I found a great jQuery solution here on SO.
var success = $.grep(array_a, function(v,i) {
return $.inArray(v, array_b) !== -1;
}).length === array_a.length;
I wish someone would post an example of how to do this in underscore.
回答16:
function in_array(needle, haystack){
return haystack.indexOf(needle) !== -1;
}
回答17:
You can simply use the "includes" function as explained in this lesson on w3schools
it looks like
let myArray = ['Kevin', 'Bob', 'Stuart'];
if( myArray.includes('Kevin'))
alert('Kevin is here');
回答18:
An equivalent of in_array with underscore is _.indexOf
Examples:
_.indexOf([3, 5, 8], 8); // returns 2, the index of 8
_.indexOf([3, 5, 8], 10); // returns -1, not found
回答19:
If you are going to use it in a class, and if you prefer it to be functional (and work in all browsers):
inArray: function(needle, haystack)
{
var result = false;
for (var i in haystack) {
if (haystack[i] === needle) {
result = true;
break;
}
}
return result;
}
Hope it helps someone :-)
来源：https://stackoverflow.com/questions/784012/javascript-equivalent-of-phps-in-array