Create AhoCorasick.js

Author: everthis

src/AhoCorasick.js

@@ -0,0 +1,89 @@
+var AhoCorasick = function (keywords) {
+  this._buildTables(keywords)
+}
+
+AhoCorasick.prototype._buildTables = function (keywords) {
+  var gotoFn = {
+    0: {},
+  }
+  var output = {}
+
+  var state = 0
+  keywords.forEach(function (word) {
+    var curr = 0
+    for (var i = 0; i < word.length; i++) {
+      var l = word[i]
+      if (gotoFn[curr] && l in gotoFn[curr]) {
+        curr = gotoFn[curr][l]
+      } else {
+        state++
+        gotoFn[curr][l] = state
+        gotoFn[state] = {}
+        curr = state
+        output[state] = []
+      }
+    }
+
+    output[state].push(word)
+  })
+
+  var failure = {}
+  var xs = []
+
+  // f(s) = 0 for all states of depth 1 (the ones just from which 0 can directly transition)
+  for (var l in gotoFn[0]) {
+    var state = gotoFn[0][l]
+    failure[state] = 0
+    xs.push(state)
+  }
+
+  while (xs.length) {
+    var r = xs.shift()
+    // for each symbol a such that g(r, a) = s
+    for (var l in gotoFn[r]) {
+      var s = gotoFn[r][l]
+      xs.push(s)
+
+      // set state = f(r)
+      var state = failure[r]
+      while (state > 0 && !(l in gotoFn[state])) {
+        state = failure[state]
+      }
+
+      if (l in gotoFn[state]) {
+        var fs = gotoFn[state][l]
+        failure[s] = fs
+        output[s] = output[s].concat(output[fs])
+      } else {
+        failure[s] = 0
+      }
+    }
+  }
+
+  this.gotoFn = gotoFn
+  this.output = output
+  this.failure = failure
+}
+
+AhoCorasick.prototype.search = function (string) {
+  var state = 0
+  var results = []
+  for (var i = 0; i < string.length; i++) {
+    var l = string[i]
+    while (state > 0 && !(l in this.gotoFn[state])) {
+      state = this.failure[state]
+    }
+    if (!(l in this.gotoFn[state])) {
+      continue
+    }
+
+    state = this.gotoFn[state][l]
+
+    if (this.output[state].length) {
+      var foundStrs = this.output[state]
+      results.push([i, foundStrs])
+    }
+  }
+
+  return results
+}