The title should explain my question.
I have an array:
a = [[1,2],[1,3],[1,4]];
How can I check if the array [1,2] is inside the array a?
5 Answers
That depends on the situation.
given
var a = [1,2], b = [1,3], c = [a,b];
We can check easily if a resides in c, if we have c to test on.
for(var i=0,d;d=c[i];i++) {
if(d === a) {
//a is inside c
}
}
or even simpler for browser that supports it (ie7 doesn't)
if(c.indexOf(a) != -1) {
//a is inside c
}
But if we only have a, and a is not a local variable and we wish to know if it exists inside any array, then we can't, since a is a reference to an object and we can't possibly know if a reference to it exists elsewhere outside our current scope.
Comments
if you have a reference, the you can use the == operator. else you have to write your own method to test values. something like this:
function someMethod(testArr, wanted){
for (i=0; i<testArr.length; i++){
if(array_diff(testArr[i], wanted).length==0 && array_diff(wanted, $subArr).length==0){
return true;
}
}
return false;
}
function array_diff(a1, a2)
{
var a=[], diff=[];
for(var i=0;i<a1.length;i++)
a[a1[i]]=true;
for(var i=0;i<a2.length;i++)
if(a[a2[i]]) delete a[a2[i]];
else a[a2[i]]=true;
for(var k in a)
diff.push(k);
return diff;
}
3 Comments
Ali
this is php, he asked about javascript
brenjt
I would re-think your answer as to not receive more down votes. He asked for javascript not php.
Ramzi Khahil
sorry, I confused it with another question. i corrected it to javascript. :)
If your array contains numbers or texts only, you can join each array into string, then compare if a string is inside the other.
var a = [[1,2],[1,3],[1,4]];
var b = [1,2]
var aStr = '@' + a.join('@') + '@'
var bStr = '@' + b.join() + '@'
if (aStr.indexOf(bStr) > -1){
alert ('b is inside a')
}else{
alert ('b is not inside a')
}
Comments
You can try this if your array elements are non-nested arrays.
return JSON.stringify([[1,2],[1,3],[1,4]]).indexOf(JSON.stringify([1,2])) > 0
This checks if the JSON representation of [1,2] is contained in the JSON representation of [[1,2],[1,3],[1,4]]
But in this case it gives a false positive
return JSON.stringify([[[1,2]],[1,3],[1,4]]).indexOf(JSON.stringify([1,2])) > 0
returns true.
Comments
You can also loop through the array object and for each of it's item you can use jQuery.isArray() to determine if the object is an array.
Comments
[[1,2]].indexOf([1,2]) === -1.