Tell me, how correctly to check the existence of a key in associative arrays?
For example:
var mydata = {
key1: '',
key2: {
subkey1: {
subkey1_1: {
value1: ''
value2" '',
},
},
subkey2: '';
},
}
if ((mydata.key2 != undefined) && (mydata.key2.subkey1 != undefined) && (mydata.key2.subkey1.subkey1_1 != undefined))
mydata.key2.subkey1.subkey1_1.value1 = 'test';
Too long and confusing
((mydata.key2 != undefined) && (mydata.key2.subkey1 != undefined) && (mydata.key2.subkey1.subkey1_1 != undefined))
I would like to use a simpler function, like
safeSet(mydata.key2.subkey1.subkey1_1.value1, 'test');
or
if (is_undefined(mydata.key2.subkey1.subkey1_1.value1) == true)
mydata.key2.subkey1.subkey1_1.value1 = 'test'; // now - error if 'mydata.key2.subkey1.subkey1_1' not exist
You can create custom function using reduce() to test if nested property exists. You can just pass key as string.
var mydata = {
key1: '',
key2: {
subkey1: {
subkey1_1: {
value1: '',
value2: '',
},
},
subkey2: ''
},
}
function safeSet(key, data) {
return key.split('.').reduce(function(r, e) {
return r ? r[e] : undefined;
}, data) != undefined
}
console.log(safeSet('key2.subkey1.subkey1_1.value1', mydata))You should use the in operator:
"key" in obj // true, regardless of the actual value
Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:
obj.hasOwnProperty("key") // true
hope this would help you.
Source: http://www.advancesharp.com/questions/628/checking-if-an-associative-array-key-exists-in-javascript