Check if array includes a value [in an efficient way]

Question

I have a variable consisting of multiple sentences separated with dots named var a. Then I want to check if Result value is equal to one of the sentences on var a:

Here is the code:

var a = "my name is jack. your name is sara. her name is joe. his name is mike";
var nameSplit = a.split(".");

console.log(nameSplit.length);
console.log(nameSplit);

var Result = "his name is mike";
var i;
for (i = 0; i < nameSplit.length; i++) { 
    if (nameSplit[i].includes(Result)) {
       console.log("Result is one of the sentences on var a");
    }
}

The code works fine .

The problem is I have no idea if this code works fast and efficient if I have 1000 sentences or 10000 sentences on var a?

Is there any modification that makes the code faster to execute?

Is there any better solution to do this?

Well, you can remove the split. You are still ultimately looking for `a.includes(Result)` - the splitting is irrelevant to the result. Other than that, you still need a linear search, so not much can be improved. — VLAZ, Jun 05 '19 at 14:50
Other than the fact that split is unneeded, you can check this post about performances: https://stackoverflow.com/questions/5296268/fastest-way-to-check-a-string-contain-another-substring-in-javascript . Felix kling did a good coverage about what is more performant about strings containing other strings. — briosheje, Jun 05 '19 at 14:51
It's unclear if partial sentences count as a match. Should this match: `his name is`? Or do you only want full matches? — Mark, Jun 05 '19 at 14:54

Khaled Osman · Accepted Answer · 2019-06-05T14:58:31.023

2

You can use Array.prototype.includes to check if an array includes a string. or String.prototype.includes to match a substring.

var a = "my name is jack. your name is sara. her name is joe. his name is mike";
var nameSplit = a.split(". ");
var Result = "his name is mike";
nameSplit.includes(Result) // true

or

var a = "my name is jack. your name is sara. her name is joe. his name is mike";
var Result = "his name is mike";
a.includes(Result) // true

edited Jun 05 '19 at 14:58

answered Jun 05 '19 at 14:51

Khaled Osman

1,251
12
17

1

You don't need to `split` at all, since includes work on strings too. – briosheje Jun 05 '19 at 14:53
1

The split is still completely irrelevant to the result. You are just doing `a.includes(Result)` with extra steps. – VLAZ Jun 05 '19 at 14:53
More specifically, this works because [`String.prototype.includes`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes) is also a thing. – Domino Jun 05 '19 at 14:57
1

the last way will result in "true" even if result = "his name is mi" – Sara Ree Jun 05 '19 at 14:59
@SaraRee but with `Result = "his name is mi"` and `a = "my name is jack. your name is sara. her name is joe. his name is mike"`, you would still get a positive using `if (nameSplit[i].includes(Result))` – VLAZ Jun 05 '19 at 15:03
I mean Khaled Osman's first code should work for me... and yes you're right... I missed that... – Sara Ree Jun 05 '19 at 15:05

score 2 · Answer 2 · answered Jun 05 '19 at 15:06

You need to ask yourself how many substring you want to find in a, if just one, then you dont need to split as split itself takes time and space. (If interested , you can further check KMP algorithm which can efficiently match word W in a string S.)

If you have a huge amount of substrings to be matched, you then can use split, which costs more space to trade off time.

score 1 · Answer 3 · answered Jun 05 '19 at 14:53

1

I think the fastest way should be with

str.indexOf('his name is mike') !== -1

but for 1k words i dont think its relevant

answered Jun 05 '19 at 14:53

axel axel

253
1
11

score 1 · Answer 4 · answered Jun 05 '19 at 14:59

Your question says you "want to check if Result value is equal to one of the sentences" but your code doesn't check for equality. It allows partial matches — for example if Result is i it matches the i in my name is jack..

If you want to match the whole sentences, you could split the sentences into a Set and then checking for matches is a constant time operation. But they'll need to be exact matches, including whitespace.

var a = "my name is jack. your name is sara. her name is joe. his name is mike";
var nameSplit = new Set(a.split(/\.\s+/g))

var Result = "his name is mike";
if (nameSplit.has(Result))  {
  console.log("Result is one of the sentences on var a");
}
  
Result = "his name is";
if (nameSplit.has(Result))  {
  console.log("Result is one of the sentences on var a");
} else {
  console.log("not in sentences")
}

Check if array includes a value [in an efficient way]

4 Answers4