How to check if a multidimensional array item is set in JS?
w[1][2] = new Array;
w[1][2][1] = new Array;
w[1][2][1][1] = 10; w[1][2][1][2] = 20; w[1][2][1][4] = 30;
How to check if w[1][2][1][3] is set?
Solution with if (typeof w[1][2][1][3] != 'undefined') doesn't work.
I don't want to use an Object instead of Array.
How to check if a multidimensional array item is set in JS?
w[1][2] = new Array;
w[1][2][1] = new Array;
w[1][2][1][1] = 10; w[1][2][1][2] = 20; w[1][2][1][4] = 30;
How to check if w[1][2][1][3] is set?
Solution with if (typeof w[1][2][1][3] != 'undefined') doesn't work.
I don't want to use an Object instead of Array.
Share Improve this question asked Jun 2, 2013 at 14:02 ColargolColargol 7694 gold badges14 silver badges26 bronze badges 8-
what about
if (w[1][2][1][3] != 'undefined')? – karthikr Commented Jun 2, 2013 at 14:06 -
that would check
w[1][2][1][3]value is the text "undefined" – Patrick Evans Commented Jun 2, 2013 at 14:06 -
In what way does the
typeofway not work? – Patrick Evans Commented Jun 2, 2013 at 14:09 - @Patrick Evans, it returns error: TypeError: w[w1][w2][w3] is undefined in code: if (typeof w[w1][w2][w3][w4] != 'undefined') { return w[w1][w2][w3][w4]; } – Colargol Commented Jun 2, 2013 at 14:20
- then you need to check each previous array element for existence before checking the others. – Patrick Evans Commented Jun 2, 2013 at 14:22
2 Answers
Reset to default 6You are not checking the previous array elements existence before checking its children as the children elements cant exist if the parent doesnt
if(
typeof(w) != 'undefined' &&
typeof(w[1]) != 'undefined' &&
typeof(w[1][2]) != 'undefined' &&
typeof(w[1][2][1]) != 'undefined' &&
typeof(w[1][2][1][3]) != 'undefined' &&
) {
//do your code here if it exists
} else {
//One of the array elements does not exist
}
The if will run the code in the else clause if it sees any of the previous elements not existing. It stops checking the others if any of the preceding checks returns false.
Here is a more generic way you can do it by extending the prototype of Array:
Array.prototype.check = function() {
var arr = this, i, max_i;
for (i = 0, max_i = arguments.length; i < max_i; i++) {
arr = arr[arguments[i]];
if (arr === undefined) {
return false;
}
}
return true;
}
w.check(1, 2, 1, 4); //will be true if w[1][2][1][4] exists
or if you don't like prototype extension you could use a separate function:
function check(arr) {
var i, max_i;
for (i = 1, max_i = arguments.length; i < max_i; i++) {
arr = arr[arguments[i]];
if (arr === undefined) {
return false;
}
}
return true;
}
check(w, 1, 2, 1, 4); //will be true if w[1][2][1][4] exists