If I have an array like this:
var array1 =
[
{"phraseId":"abc",
"keyword":"bb",
"posId":1},
{"phraseId":"def",
"keyword":"bb",
"posId":1},
]
How can I find out that the object with phraseId of "def" has the 2nd position?
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1Possible duplicate: stackoverflow.com/questions/7364150/…Leroy Thompson– Leroy Thompson2016-08-01 18:34:39 +00:00Commented Aug 1, 2016 at 18:34
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Why you can not use a loop?Mario Santini– Mario Santini2016-08-01 18:36:03 +00:00Commented Aug 1, 2016 at 18:36
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4 Answers
You could map your object and only return the target field, and then use the built in indexOf to get the position:
array1.map(item => item.phraseId).indexOf('def')
1 Comment
Ryan Wheale
Not downvoting, but this results in 2 iterations of the array as well as the allocation of more memory for the 2nd mapped array, which is unnecessary.
Use native JavaScript findIndex method.
var array1 = [{
"phraseId": "abc",
"keyword": "bb",
"posId": 1
}, {
"phraseId": "def",
"keyword": "bb",
"posId": 1
}, ];
var pos = array1.findIndex(function(v) {
// set your condition for finding object
return v.phraseId == 'def';
// add `1` since you want to count from `1`
}) + 1;
console.log("Position of the object " + pos);For older browser check polyfill option.
With ES6 arrow function
var array1 = [{
"phraseId": "abc",
"keyword": "bb",
"posId": 1
}, {
"phraseId": "def",
"keyword": "bb",
"posId": 1
}, ];
var pos = array1.findIndex(v => v.phraseId == 'def') + 1;
console.log("Position of the object " + pos);
3 Comments
StriplingWarrior
I did not know that
findIndex was an official ECMAScript 6 thing. Neat.
semanser
I think this solution better than
.map() because findIndex() it's native JS method returns an index in the array unlike .map wich used for array iteration. Interesting to see some benchmarks of this two methods.Ryan Wheale
Since we're using the latest cool stuff, why not write it the easy way:
var pos = array1.findIndex(v => v.phraseId === 'def');It works this way :
array1.forEach((elem, index) => {if (elem.phraseId === "def")
console.log("index = " + index);
});
Comments
Assuming that your key is know (that you know you are looking for a phraseId always) then you can simply iterate through the array with a normal for loop if you are using "traditional" JS, or with a forEach if you are using ES6. Here's the simple for implementation.
for (var i = 0; i < array1.length; i++ ){
if(array[i].phraseId === 'def') {
// we know "i" is the index, so do something...
}
}
To make it more generic so you can search any array for any key, make a function of it that returns the index:
function whatIndex (arr, key, val) {
for (var i = 0; i < arr.length; i++) {
if( arr[i][key] === val ) {
return i;
}
}
}
