How can i check if a particular key exists in a JavaScript array?
Actually, i am checking for undefinedness for whether a key exists. What if the key exists but the value is actually undefined?
var obj = { key: undefined }; obj["key"] != undefined // false, but the key exists!
With in operator.
0 in [10, 42] // true
2 in [10, 42] // false
'a' in { a: 'foo' } // true
'b' in { a: 'foo' } // false
Use the in operator.
if ( "my property name" in myObject )
let $arr = [1, 0, false];
console.log($arr.indexOf(0)); // 1
console.log($arr.indexOf(false)); // 2
console.log($arr.indexOf(15)); // -1
if ($arr.indexOf(18) !== -1) //Todo
You can use the Javascript array filter funtion. Like that:
const arr = ["ab","cd"]
const needle = "cd"
console.log( arr.filter(i => i == needle).length > 0 ? "exists" : "not exists" )Use hasOwnProperty(key)
for (let i = 0; i < array.length; i++) {
let a = obj[i].hasOwnProperty(`${key}`);
if(a){
console.log(obj[i])
}
}
