提供JavaScript版本的《实现strStr()》

problems/0028.实现strStr.md

@@ -808,7 +808,93 @@ func strStr(haystack string, needle string) int {
 }
 ```
 
+JavaScript版本
 
+> 前缀表统一减一
+
+```javascript
+/**
+ * @param {string} haystack
+ * @param {string} needle
+ * @return {number}
+ */
+var strStr = function (haystack, needle) {
+    if (needle.length === 0)
+        return 0;
+
+    const getNext = (needle) => {
+        let next = [];
+        let j = -1;
+        next.push(j);
+
+        for (let i = 1; i < needle.length; ++i) {
+            while (j >= 0 && needle[i] !== needle[j + 1])
+                j = next[j];
+            if (needle[i] === needle[j + 1])
+                j++;
+            next.push(j);
+        }
+
+        return next;
+    }
+
+    let next = getNext(needle);
+    let j = -1;
+    for (let i = 0; i < haystack.length; ++i) {
+        while (j >= 0 && haystack[i] !== needle[j + 1])
+            j = next[j];
+        if (haystack[i] === needle[j + 1])
+            j++;
+        if (j === needle.length - 1)
+            return (i - needle.length + 1);
+    }
+
+    return -1;
+};
+```
+
+> 前缀表统一不减一
+
+```javascript
+/**
+ * @param {string} haystack
+ * @param {string} needle
+ * @return {number}
+ */
+var strStr = function (haystack, needle) {
+    if (needle.length === 0)
+        return 0;
+
+    const getNext = (needle) => {
+        let next = [];
+        let j = 0;
+        next.push(j);
+
+        for (let i = 1; i < needle.length; ++i) {
+            while (j > 0 && needle[i] !== needle[j])
+                j = next[j - 1];
+            if (needle[i] === needle[j])
+                j++;
+            next.push(j);
+        }
+
+        return next;
+    }
+
+    let next = getNext(needle);
+    let j = 0;
+    for (let i = 0; i < haystack.length; ++i) {
+        while (j > 0 && haystack[i] !== needle[j])
+            j = next[j - 1];
+        if (haystack[i] === needle[j])
+            j++;
+        if (j === needle.length)
+            return (i - needle.length + 1);
+    }
+
+    return -1;
+};
+```