compare strings and get end difference

Question

I have two strings.
String A: "The quick brown fox"
String B: "The quick brown fox jumps over the lazy dog."

String B will always contain string A verbatim. There will never be a "quick black fox" or a "quick and speedy brown fox".

How do I get a "String C" of the difference "jumps over the lazy dog."?

Homework? Anyways, a simple way is to start with a length variable (call it `l` or something) and run a loop that sees if `strA.substring(0,l) == strB.substring(0,l)` untill it doesnt. Then, return `strB.substring(l);`. — Alxandr, Nov 05 '11 at 23:32
My answer works. It writes all the differences in the string. Look below — comu, Nov 05 '11 at 23:47

Mateja Petrovic · Answer 1 · 2019-07-23T18:48:14.397

44

const A = "The quick brown fox"

const B = "The quick brown fox jumps over the lazy dog."

const diff = (diffMe, diffBy) => diffMe.split(diffBy).join('')

const C = diff(B, A)

console.log(C) // jumps over the lazy dog.

edited Jul 23 '19 at 18:48

answered Jun 30 '18 at 18:46

Mateja Petrovic

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Good eye, Mateja, VERY elegant solution for the OPs problem. d-d-d-d-d-efinitely should be the accepted answer (with just one modification maybe): Since the OP didn't state however where within string A string B will occur (even though the example had it at the beginning), it would be good to examine B.split(A)[0] as well. – KevinHJ Jul 31 '18 at 01:26
What I meant was, A="the lazy dog", B="The quick brown fox jumps over the lazy dog", arr=B.split(A), console.log(arr[0] + arr[1]) // "The quick brown fox jumps over" – KevinHJ Aug 01 '18 at 00:49
1

Simply joining arr[0] and arr[1] will always give the difference whether the partial string is at the beginning, end, or middle. – KevinHJ Aug 01 '18 at 00:57
1

Great for guarenteed substrings, but does not work for middle-diffs. What about `diff("AAAAA", "AABAA")`? There is no exact match, and thus you will get no splits, returning the original string. Perhaps the wrong problem that OP, however. – mix3d Dec 04 '18 at 21:19
@mix3d What would you like `diff("AAAAA", "AABAA")` to return? – Mateja Petrovic Dec 05 '18 at 15:30
1

This also does not handle string with multiple whitespace characters – Hunter Monk Apr 15 '20 at 03:44

score 12 · Answer 2 · edited Mar 26 '18 at 18:36

12

See the basic example below. This can easily be modified/extended for different behaviour.

var stringA = document.getElementById('string_a').textContent,
    stringB = document.getElementById('string_b').textContent,
    firstOccurrence = stringB.indexOf(stringA);

if(firstOccurrence === -1)
{
  alert('Search string Not found');
}
else
{
  var stringALength = stringA.length;
  var newString;

  if(firstOccurrence === 0)
  {
    newString = stringB.substring(stringALength);
  }
  else
  {
    newString = stringB.substring(0, firstOccurrence);
    newString += stringB.substring(firstOccurrence + stringALength);
  }

  document.getElementById('diff').textContent = newString;
}

<p>String A: <span id="string_a">The quick brown fox</span></p>
<p>String B: <span id="string_b">The quick brown fox jumps over the lazy dog</span></p>
<hr/>
<p>Difference: <span id="diff"></span></p>

edited Mar 26 '18 at 18:36

Rory O'Kane

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answered Nov 06 '11 at 01:24

Ghost-Man

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I used to be a computer science tutor (or, in the US, a 'TA'). This would be the only answer I'd award full marks to. It ought to be the accepted answer. – Michael Scheper Aug 19 '15 at 15:14
@MichaelScheper I agree, this should be the accepted answer, I have formatted for better readability and turned into runnable code snippet – doz87 Jan 23 '17 at 21:01
1

Nice one, @doz87! Suggestions for further improvement: use the identity operator instead of equality operator http://stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons and camelCase variable names instead of ones with_underscores http://www.w3schools.com/js/js_conventions.asp But neither of these issues affect the correctness nor usefulness of this answer. – Michael Scheper Jan 24 '17 at 01:38
@MichaelScheper Absolutely agree with your suggestions, I'll admit.. I was being lazy :) but I've updated the answer now – doz87 Jan 24 '17 at 04:53
@doz87: I'm still seeing underscores and equality operators. Perhaps your changes didn't save? ☹ Again, it's not a big deal, but thanks for the effort—the more examples we create that follow good coding standards, the better all the code in the world will get. ☺ – Michael Scheper Feb 07 '17 at 00:22

score 10 · Answer 3 · answered Sep 14 '18 at 17:18

10

If "String B will always contain string A verbatim", won't the following suffice?

var c = b.replace(a, "");

answered Sep 14 '18 at 17:18

kc2001

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it's 2023, and this solves my problem. – booluw Aug 27 '23 at 19:11

score 8 · Answer 4 · edited Dec 24 '19 at 12:22

8

You need to cross check each word to the other one.

var s1 = "The quick brown fox",
  s2 = "The quick brown fox jumped over the fence",
  string1 = new Array(),
  string2 = new Array(),
  diff = new Array(),
  longString;

string1 = s1.split(" ");
string2 = s2.split(" ");

if (s1.length > s2.length) {
  longString = string1;
} else {
  longString = string2;
}

for (x = 0; x < longString.length; x++) {
  if (string1[x] != string2[x]) {
    diff.push(string2[x]);
  }
}

document.write("The difference in the strings is " + diff.join(" "));

edited Dec 24 '19 at 12:22

Tushar Walzade

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answered Nov 05 '11 at 23:45

comu

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"string B will always contain string A verbatim" means "don't check word by word" – Kenan Banks Nov 06 '11 at 00:00
Will it always be an extension, or could string A be anywhere in string B. – comu Nov 06 '11 at 01:13
You misinterpreted the question. In your answer s1 and s2 would be wrong because s2 doesn't contain s1. – Andy Ray Nov 06 '11 at 01:39
1

It may work, but again, it's grossly inefficient and unnecessarily complicated. – Michael Scheper Aug 19 '15 at 15:13

chim · Answer 5 · 2015-08-20T08:37:25.257

7

comu's answer as a function...

function compareString( s1, s2, splitChar ){
    if ( typeof splitChar == "undefined" ){
        splitChar = " ";
    }
    var string1 = new Array();
    var string2 = new Array();

    string1 = s1.split( splitChar );
    string2 = s2.split( splitChar );
    var diff = new Array();

    if(s1.length>s2.length){
        var long = string1;
    }
    else {
        var long = string2;
    }
    for(x=0;x<long.length;x++){
        if(string1[x]!=string2[x]){
            diff.push(string2[x]);
        }
    }

    return diff;    
}
compareString( "?Yo=dude", "?Yo=Dude&do=roby", "&" ).join('\n');
compareString( "?Yo=Dude", "?Yo=Dude&do=roby", "&" ).join('\n');

Note: this answer solves the issue of finding extra query parameters (based on another query string), and is not an exact answer for the OP.

edited Aug 20 '15 at 08:37

answered Nov 25 '11 at 10:42

chim

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That's quite an overengineered solution!! ~Ghost-Man's solution is at least an order of magnitude more efficient! http://stackoverflow.com/a/8024608/1450294 – Michael Scheper Aug 19 '15 at 15:10
2

That's a fair comment @Michael I haven't answered the original question, but posted a solution to the problem that I had at the time. I think I must have done this as this was the problem I was trying to solve and it was comu's answer that helped me, so I posted the code I used. I'll update my answer to reflect that it doesn't answer the question exactly. – chim Aug 20 '15 at 08:34
2

I commend your StackOverflow integrity. :-) – Michael Scheper Aug 20 '15 at 14:57

score 4 · Answer 6 · answered Apr 06 '15 at 06:49

4

Check out this site for a wonderful API to see the difference between strings: google-diff-match-patch You might need to check the UI according to your need though.

answered Apr 06 '15 at 06:49

akshay

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score 1 · Answer 7 · edited Jun 04 '21 at 04:57

1

const str1 = "The quick brown fox jumps over the lazy dog.";
const str2 = "he quick brown fox";

res = Str1.split(str2).join('');

edited Jun 04 '21 at 04:57

greybeard

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answered Jun 04 '21 at 02:53

Dhole Hari

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(Try pasting that into a Python interpreter.) (Some interpretation of `end difference` - not that the question was exemplary consistent.) – greybeard Jun 04 '21 at 05:04

score 0 · Answer 8 · answered Feb 25 '19 at 09:23

I found the simple way.

Here is the code:

var t1 = "The quick brown fox";
var t2 = "The quick brown fox jumps over the lazy dog.";
var indxFoundStart = t2.search(t1); //first index of the position of t1 found in t2 (not use but you can print for sure)
var indxFoundEnd = t1.length; //last index of t1 found in t2
var textCompareLen = t2.length; // length of the longer string

// You can add the condition to verify which text is shorter, which text is longer if you do not want to fixed in t1 and t2
document.write("difference string is: " + t2.substring(indxFoundEnd, textCompareLen));

I have try with 2 sample, the text with space and the text without space and it work fine.

Absolutely, I have try with your example, and it work fine too.

score 0 · Answer 9 · answered May 08 '22 at 11:11

0

You can just use String.prototype.replace() :

var string1 = "The quick brown fox"
    
var string2 = "The quick brown fox jumps over the lazy dog."
    
var diff = ''
    
diff = string2.replace(string1, '')
    
console.log(diff)

answered May 08 '22 at 11:11

Taher ben abdallah

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compare strings and get end difference

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