Check if string contains substring without using indexOf - Javascript

Question

My function is trying to check if string contains substring without use of indexOf or regex match or any standard JS methods.

Please check this jsfiddle: https://jsfiddle.net/09x4Lpj2/

var string1 = 'applegate';
    var string2 = 'gate';

    function containsString(string1, string2){
	  var j = 0;
      var k = 0;
      var contains = 'false';
      var charArray1 = string1.split('');
      var charArray2 = string2.split('');
  
      for(var i = 0; i < charArray2.length; i++){
  	    j = i;
        if(charArray1[j++] != charArray2[k++]){
    	  contains = 'false';
        }else{
    	  contains = 'true';
        }   
      }
  
     console.log(contains);
    }
containsString(string1, string2);

This solution works only when the indexes are the same between the two strings (ex. applegate and apple). But will not work if the indexes are not the same (ex. applegate and gate). How do I manipulate the iterative values correctly so that the function returns true for both situations?

there is not need to convert string to char array. string is already char array — Bryan Chen
– Bryan Chen, Commented Oct 17, 2016 at 0:29

am05mhz · Accepted Answer · 2021-06-18 05:49:30Z

you can try this modified script of yours.

var string1 = 'applegate';
var string2 = 'gate';
var string3 = 'apple';
var string4 = 'leg';
var string5 = 'banana';

function containsString(string1, string2){
  var charArray1 = string1.split('');
  var charArray2 = string2.split('');
  var match = 0;

  // iterate from start of 1st string until length of 1st string minus length of 2nd string
  // you don't need to iterate the last part that is not longer than 2nd string since it will be false
  for(var i = 0; i < charArray1.length - charArray2.length + 1; i++){
    // reset match counter on every iteration
    match = 0;
    // iterate the 2nd string
    for(var j = 0; j < charArray2.length; j++){
      // compare corresponding char location
      if(charArray1[i+j] == charArray2[j]){
        match++;
        // just to check in console
        console.log(i, j, match, charArray1[i+j], charArray2[j]);
      } else {
        // just to check in console
        console.log(i, j, match, charArray1[i+j], charArray2[j]);
        // if not match, just skip current check
        break;
      }
      // if match already found, stop the checks, and return true
      if(match == charArray2.length){
        return true;
      }
    }
  }
  // match not found until end of iteration
  return false;
}

console.log(containsString(string1, string2));
console.log(containsString(string1, string3));
console.log(containsString(string1, string4));   
console.log(containsString(string1, string5));   // haystack does not contain needle
console.log(containsString(string4, string1));   // haystack is shorter than needle

Thanks you. This is really helpfull. Especially for environments that doesn't support indexOf method like IE < 9 etc...

Searching · Accepted Answer · 2016-10-17 00:34:05Z

1

Welcome to SO. Regex can be used.. Unless even that is also prohibited..

 function containsString(string1, string2){
    console.log(string1.match(string2) != null ? "Yes" : "No");
 }

Regex

edited Oct 17, 2016 at 0:34

answered Oct 17, 2016 at 0:30

Searching

2,2791 gold badge17 silver badges28 bronze badges

3 Comments

qollers Over a year ago

thank you for the alternative solution :) however, i am trying my best to avoid regex match or any other methods so that I can develop an algorithm for this type of situation.

Nayuki Over a year ago

This will not work if string2 contains regex metacharacters like .*[]()

Searching Over a year ago

Ya agreed. But apparently Regex is out of question..So this cannot be THE Answer.. just a starting point. : )

遁地龙卷风 · Accepted Answer · 2016-10-17 00:54:57Z

0

This code has a logical problem，Only to determine whether the last character of A is equal to the corresponding character of B，Maybe the following code is what you want,add a line of code.

var string1 = 'applegate';
var string2 = 'gate';

function containsString(string1, string2){
  var j = 0;
  var k = 0;
  var contains = 'false';
  var charArray1 = string1.split('');
  var charArray2 = string2.split('');

  for(var i = 0; i < charArray2.length; i++){
    j = i;
    if(charArray1[j++] != charArray2[k++]){
      contains = 'false';
      break;
    }else{
      contains = 'true';
    }   
  }

 console.log(contains);
}

answered Oct 17, 2016 at 0:54

遁地龙卷风

404 bronze badges

Comments

shubhs · Accepted Answer · 2020-03-16 13:42:03Z

0

Check this without using any inbuilt functions

function subSearch(long,short){
var count = 0
for(i = 0;i < long.length; i++){
  for(j = 0;j < short.length; j++){
    if(short[j] != long[i + j]){
      break;
    }
    if((j+1) == short.length){
      count++;
    }
  }
}
return count;
}

answered Mar 16, 2020 at 13:42

shubhs

363 bronze badges

Collectives™ on Stack Overflow

Check if string contains substring without using indexOf - Javascript

4 Answers 4

1 Comment

3 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

3 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related