How to find index of object in array without iterating in javascript

Question

Lets have an sample array like [1,2,3,4,5,6,7,8,9,10,12,0, 1, 2, 3,4 ]

I want to find the first occurrence of ' 0 ' in this array, but without iterating the same.

all the functions 'like', 'map', 'grep', 'filter', 'some','for each' everything iterating every element in the array to find the same. Considering big data array's its very much bottleneck considering performance.

I have tried all the above methods. Anybody has any idea about this?. Thanks for your time.

• rajuGT: without doing any search operation, how can you search? Atleast use something like hashtables may help
• Teemu: You simply can't achieve this with an array. Even native indexOf does internal iteration.
• Alex K.: You can reduce the iteration count, E.g. if the data were sorted, but some iteration is always going to happen.
• vbranden: Try a Middle out approach

Answer 1

How to find index of object in array without iterating in javascript

This is impossible. If you have a generic list of values, you have to look at each element until you find the one you are looking for.

If you want O(1) access then you need to use a different data structure.

• Karthikvenkat86: I wonder how bigData systems and analytics handle this situation when they huge list. Won't their performace affect for each search
• fuyushimoya: @Karthikvenkat86 They may slice the data into fragments and use some hash to reduce time. Upvoted, as it should be the answer for that question.
• Felix Kling: Such data sets have probably multiple indexes defined for them to allow efficient access via different set of search parameters. Just think about a simple database table. The primary key is always indexed for efficient access. An index is nothing but an id -> value mapping.
• Sachin: Usually Big Data is not handled in javascript. Most popular Big Data techniques involve map/reduce or slicing it to arrive at the desired results
• Felix Kling: Also the operation may be parallelizable, like map/reduce.

Answer 2

If the elements of the array is a number or string, you can just use indexOf()

indexOf() compares searchElement (first parameter) to elements of the Array using strict equality (the same method used by the ===, or triple-equals, operator).

var list = [1,2,3,4,5,6,7,8,9,10,12,0, 1, 2, 3,4 ];
var firstOccurence = list.indexOf(0);

• rajuGT: indexOf would internally iterate the array elements. The OP is asking which doesnt iterate over array.
• Sachin: Doesn't indexOf iterate the array as well? as per ecma-international.org/ecma-262/5.1/#sec-15.4.4.14
• Griffith: Absolutely. There is a significant difference between internal iteration handled by the browser and the callback arguments provided by methods such as map() or filter() though