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Task/Jaro-Winkler-distance/TypeScript/jaro-winkler-distance.ts

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+var fs = require('fs')
+
+// Jaro Winkler Distance Formula
+function jaroDistance(string1: string, string2: string): number{
+    // Compute Jaro-Winkler distance between two string
+    // Swap strings if string1 is shorter than string 2
+    if (string1.length < string2.length){
+        const tempString: string = string1;
+        string1 = string2;
+        string2 = tempString
+    }
+    let len1: number = string1.length
+    let len2: number = string2.length
+    if (!len2){
+        return 0.0
+    }
+    const delta: number = Math.max(1, len1 / 2.0) - 1.0;
+    // Flags for transpositions
+    let flag: boolean[] = Array(len2).fill(false)
+    let ch1Match: string[] = Array(len1).fill('')
+    // Count number of matching characters
+    let matches = 0
+    // Check if characters on both string matches
+    for (let i: number = 0; i < len1; i++){
+            const ch1: string = string1[i]
+            for (let j = 0; j < len2; j++){
+                const ch2: string = string2[j]
+                if (j <= i + delta && j + delta >= 1 && ch1 == ch2 && !flag[j]){
+                    flag[j] = true
+                    ch1Match[matches++] = ch1;
+                    break;
+                }
+            }
+    }
+    if (!matches){
+        return 1.0
+    }
+    // Count number of transpositions (shared characters placed in different positions)
+    let transpositions: number = 0.0
+    for (let i: number = 0, j: number = 0; j < len2; j++){
+            if (flag[j]){
+                if (string2[j] != ch1Match[i]){
+                    transpositions++
+                }
+                i++
+            }
+    }
+    const m: number = matches
+    // Jaro Similarity Formula simj = ( (m / length of s1) + (m / length of s2) + (m - t) / m ) / 3
+    const jaro: number = (m / len1 + m / len2 + (m - transpositions / 2.0) / m) / 3.0
+    // Length of common prefix between string up to 4 characters
+    let commonPrefix: number = 0.0
+    len2 = Math.min(4, len2)
+    for (let i: number = 0; i < len2; i++){
+        if (string1[i] == string2[i]){
+            commonPrefix++
+        }
+    }
+    // Jaro Winkler Distance Formula simw = simj + lp(1 - simj)
+    return 1.0 - (jaro + commonPrefix * 0.1 * (1.0 - jaro))
+}
+
+// Compute Jaro Winkler Distance for every word on the dictionary against the misspelled word
+function withinDistance(words: string[] ,maxDistance: number, string: string, maxToReturn: number): (string | number)[][]{
+    let result: (string | number)[][]  = new Array()
+    words.forEach(word =>{
+        const distance = jaroDistance(word, string)
+        // check if computed jaro winkler distance is within the set distance parameter
+        if (distance <= maxDistance){
+            const tuple = [distance, word]
+            result.push(tuple)
+        }
+    })
+    result.sort()
+    // Limit of matches set to maxtoReturn
+    return result.length <= maxToReturn ? result : result.slice(0, maxToReturn)
+}
+
+function loadDictionary(fileName: string): string[]{
+    let words: string[] = new Array()
+    try{
+        //attacomsian.com/blog/reading-a-file-line-by-line-in-nodejs
+        const data = fs.readFileSync(fileName, 'utf-8')
+        const lines: string[] = data.split(/\r?\n/)
+        lines.forEach(line => {
+            words.push(line)
+        })
+        return words
+    }
+    catch(error){
+        console.log("Error reading dictionary")
+    }
+}
+
+function main(): void{
+    try {
+        const misspellings = [
+            "accomodate​",
+            "definately​",
+            "goverment",
+            "occured",
+            "publically",
+            "recieve",
+            "seperate",
+            "untill",
+            "wich"
+        ]
+        //unixdict.txt from users.cs.duke.edu/~ola/ap/linuxwords
+        let words: string[] = loadDictionary("unixdict.txt")
+
+        misspellings.forEach(spelling =>{
+            console.log("Misspelling:", spelling)
+            const closeWord = withinDistance(words, 0.15, spelling, 5)
+            closeWord.forEach(word =>{
+                console.log((word[0] as number).toFixed(4) + " " + word[1])
+            })
+            console.log("")
+        })
+    }
+    catch(error) {
+        console.log("Error on main")
+    }
+}
+main();