Filter null from an array in JavaScript
JavascriptArraysJavascript Problem Overview
I have a task to remove false, null, 0, "", undefined, and NaN elements from an given array. I worked on a solution which removes all except null. Anyone can explain why? Here's the code:
function bouncer(arr) {
var notAllowed = ["",false,null,0,undefined,NaN];
for (i = 0; i < arr.length; i++){
for (j=0; j<notAllowed.length;j++) {
arr = arr.filter(function(val) {
return val !== notAllowed[j];
});
}
}
return arr;
}
bouncer([1,"", null, NaN, 2, undefined,4,5,6]);
Javascript Solutions
Solution 1 - Javascript
Well, since all of your values are falsy, just do a !! (cast to boolean) check:
[1,"", null, NaN, 2, undefined,4,5,6].filter(x => !!x); //returns [1, 2, 4, 5, 6]
Edit: Apparently the cast isn't needed:
document.write([1,"", null, NaN, 2, undefined,4,5,6].filter(x => x));
And the code above removes "", null, undefined and NaN just fine.
Solution 2 - Javascript
It is a problem with NaN, because
NaN !== NaN
read more here: Testing against NaN.
For filtering the values, you could check for truthyness.
function bouncer(arr) { return arr.filter(Boolean); }
console.log(bouncer([1, "", null, NaN, 2, undefined, 4, 5, 6]));
Solution 3 - Javascript
You can use Array.prototype.filter for truthy value check - see demo below:
function bouncer(array) {
return array.filter(function(e) {
return e;
});
}
console.log(bouncer([1,"", null, NaN, 2, undefined,4,5,6]));
Solution 4 - Javascript
[1, 2, 0, null, "sdf", ""].filter(a=>a)
// filter non null value, remove 0, null and "" (empty quote)
console.log([1, 2, 0, null, "sdf", ""].filter(a=>a))
Solution 5 - Javascript
Use
function bouncer(arr) {
return arr.filter(function(item){
return !!item;
});
}
console.log(bouncer([1,"", null, NaN, 2, undefined,4,5,6]));