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Javascript - How to know how much string matched in another string?

I have been implementing a simple quiz for English. In that, we need to validate answers, which are entered by users in input field. In the current implementation, I am comparing the correct answer with user's answer exactly. Like,

HTML

<input type="text" id="answer" />
<button onclick="validate()">Validate</button>


Javascript

var question = "Do you like movies?",
answer = "No, I don't like movies.";

function validate()
var userInput = document.getElementById('answer').value;
if(answer == userInput)
console.log("correct");
else
console.log("wrong");




But I don't want validate exactly. Like, ignore case sensitive, commas, apostrophe, etc. For example if user enters,

i dont like movies

The answer can be correct. I don't know how start and where to start. Anyone please help.

2 Answers
2

One option would be to strip out all non-word characters and spaces, and compare the lower-case version of each replaced string:

var question = "Do you like movies?",
answer = "No, I don't like movies.";

const normalize = str => str
.replace(/[^w ]/g, '')
.toLowerCase();
function validate(userInput)
const noramlizedInput = normalize(userInput)
const noramlizedAnswer = normalize(answer);
if (noramlizedInput == noramlizedAnswer)
console.log("correct");
else
console.log("wrong");


validate('No i dont like movies');
validate("NO!!!!! I DON''t like movies.");

Another option would be to loop through all possible substrings of the userInput and figure out which has the most overlap with the desired answer, but that's a whole lot more complicated.

userInput

answer

An easier option would be to check to see how many overlapping words there are:

var question = "Do you like movies?",
answer = "No, I don't like movies.";

const normalize = str => str
.replace(/[^w ]/g, '')
.toLowerCase()
.split(/s+/)
function validate(userInput)
const noramlizedInputArr = normalize(userInput);
const noramlizedAnswerArr = normalize(answer);
const overlapCount = noramlizedInputArr.reduce((a, word) => (
a + Number(noramlizedAnswerArr.includes(word))
), 0);
console.log(overlapCount);
if (overlapCount >= 4)
console.log("correct");
else
console.log("wrong");


validate('No i dont like movies');
validate("NO!!!!! I DON''t like movies.");
validate("i dont like movies.");
validate("Yes I like movies.");

dont

do not

Nah, I do not enjoy movies

Yes

If you are interested in simply catching spelling errors and small variations, a standard metric is called edit distance or Levenshtein distance. This is a count of the minimum number of deletions, insertions, or substitutions you need to change one text into another. Strings like "No I don't like the movies" and "No I don't like the moveys" will have small edit distances.

Here's a quick and dirty recursive edit distance function that will give you an idea:

function validate(text, pattern)
// some simple preprocessing
let p = pattern.toLowerCase().replace(/[^a-z]+/ig, '')
let t= text.toLowerCase().replace(/[^a-z]+/ig, '')

// memoize recursive algorithm
let matrix = Array.from(length: t.length + 1, () => )

function editDistance(text, pattern, i = 0, j = 0) (matrix[i][j+1] = editDistance(text, pattern, i, j+1))) + 1
]
return Math.min(...choices)

return editDistance(t, p)


// similar strings have smaller edit distances
console.log(validate("No I dont lik moves","No i dont like movies"))

// a little less similar
console.log(validate("Yes I like movies","No i dont like movies"))

// totally different
console.log(validate("Where is the bathroom","No i dont like movies"))

// careful -- small edit distance !== close meaning
console.log(validate("I do like tacos","I don't like tacos"))

Picking a minimum acceptable distance works pretty well for matching strings with small typos. Of course, if you are trying to gauge user intent, none of these simple hues tics will work. Strings like "I love tacos" and "I loath tacos" have a small edit distance and you can't tell that they mean the opposite without knowledge of the language. If you need to do this level of checking you can try using a service like Watson Conversation that will return user intents to input.

Watson Conversation

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