Implementing hash table

Author: ChauDinh

Data Structures/Hash Tables/index.js

@@ -0,0 +1,67 @@
+function hashStringToInt(str, tableSize) {
+  let hash = 17;
+
+  for (let i = 0; i < str.length; i++) {
+    hash = (13 * hash * str.charCodeAt(i)) % tableSize;
+  }
+
+  return hash;
+}
+
+class HashTable {
+  table = new Array(3);
+  numItems = 0;
+
+  resize = () => {
+    const newTable = new Array(this.table.length * 2);
+    this.table.forEach(item => {
+      if (item) {
+        item.forEach(([key, value]) => {
+          const idx = hashStringToInt(key, newTable.length);
+          if (newTable[idx]) {
+            newTable[idx].push([key, value]);
+          } else {
+            newTable[idx] = [[key, value]];
+          }
+        });
+      }
+    });
+    this.table = newTable;
+  };
+
+  setItem = (key, value) => {
+    this.numItems++;
+    const loadFactor = this.numItems / this.table.length;
+
+    if (loadFactor > 0.1) {
+      // resize the table
+      this.resize();
+    }
+
+    const idx = hashStringToInt(key, this.table.length);
+    if (this.table[idx]) {
+      this.table[idx].push([key, value]);
+    } else {
+      this.table[idx] = [[key, value]];
+    }
+  };
+
+  getItem = key => {
+    const idx = hashStringToInt(key, this.table.length);
+    return this.table[idx].find(x => x[0] === key)[1];
+    // the Array.prototype.find() returns the first element in the array satisfies the test function
+  };
+}
+
+const newHashTable = new HashTable();
+
+newHashTable.setItem("lastName", "tim");
+newHashTable.setItem("firstName", "bob");
+newHashTable.setItem("age", 24);
+newHashTable.setItem("dob", "2/2/2");
+// newHashTable.setItem("adress", "123/123/123");
+console.log(newHashTable.getItem("firstName"));
+console.log(newHashTable.getItem("lastName"));
+console.log(newHashTable.getItem("dob"));
+console.log(newHashTable.table.length);
+console.log(newHashTable.table);