Create 1472-design-browser-history.js

Author: everthis

1472-design-browser-history.js

@@ -0,0 +1,57 @@
+/**
+ * @param {string} homepage
+ */
+const BrowserHistory = function(homepage) {
+  this.idx = 0
+  this.arr = [homepage]
+};
+
+/** 
+ * @param {string} url
+ * @return {void}
+ */
+BrowserHistory.prototype.visit = function(url) {
+  const n = this.arr.length
+  this.arr.splice(this.idx + 1, n - this.idx - 1, url)
+  this.idx++
+};
+
+/** 
+ * @param {number} steps
+ * @return {string}
+ */
+BrowserHistory.prototype.back = function(steps) {
+  const idx = this.idx
+  let tmp = idx - steps
+  if(tmp < 0) {
+    this.idx = 0
+    return this.arr[0]
+  } else {
+    this.idx = tmp
+    return this.arr[tmp]
+  }
+};
+
+/** 
+ * @param {number} steps
+ * @return {string}
+ */
+BrowserHistory.prototype.forward = function(steps) {
+  const n = this.arr.length
+  let tmp = this.idx + steps
+  if(tmp >= n) {
+    this.idx  = n - 1
+    return this.arr[n - 1]
+  } else {
+    this.idx = tmp
+    return this.arr[tmp]
+  }
+};
+
+/** 
+ * Your BrowserHistory object will be instantiated and called as such:
+ * var obj = new BrowserHistory(homepage)
+ * obj.visit(url)
+ * var param_2 = obj.back(steps)
+ * var param_3 = obj.forward(steps)
+ */