diff --git a/Data Structures/isSubsetOf.js b/Data Structures/isSubsetOf.js
new file mode 100644
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+++ b/Data Structures/isSubsetOf.js	
@@ -0,0 +1,92 @@
+// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/perform-a-subset-check-on-two-sets-of-data
+
+class Set {
+  constructor() {
+    // This will hold the set
+    this.dictionary = {};
+    this.length = 0;
+  }
+  // This method will check for the presence of an element and return true or false
+  has(element) {
+    return this.dictionary[element] !== undefined;
+  }
+  // This method will return all the values in the set
+  values() {
+    return Object.keys(this.dictionary);
+  }
+  // This method will add an element to the set
+  add(element) {
+    if (!this.has(element)) {
+      this.dictionary[element] = true;
+      this.length++;
+      return true;
+    }
+
+    return false;
+  }
+  // This method will remove an element from a set
+  remove(element) {
+    if (this.has(element)) {
+      delete this.dictionary[element];
+      this.length--;
+      return true;
+    }
+
+    return false;
+  }
+  // This method will return the size of the set
+  size() {
+    return this.length;
+  }
+  // This is our union method
+  union(set) {
+    const newSet = new Set();
+    this.values().forEach((value) => {
+      newSet.add(value);
+    });
+    set.values().forEach((value) => {
+      newSet.add(value);
+    });
+
+    return newSet;
+  }
+  // This is our intersection method
+  intersection(set) {
+    const newSet = new Set();
+
+    let largeSet;
+    let smallSet;
+    if (this.dictionary.length > set.length) {
+      largeSet = this;
+      smallSet = set;
+    } else {
+      largeSet = set;
+      smallSet = this;
+    }
+
+    smallSet.values().forEach((value) => {
+      if (largeSet.dictionary[value]) {
+        newSet.add(value);
+      }
+    });
+
+    return newSet;
+  }
+
+  difference(set) {
+    const newSet = new Set();
+
+    this.values().forEach((value) => {
+      if (!set.dictionary[value]) {
+        newSet.add(value);
+      }
+    });
+
+    return newSet;
+  }
+  // Only change code below this line
+  isSubsetOf(otherSet) {
+    return this.values().every((item) => otherSet.has(item));
+  }
+  // Only change code above this line
+}