fix(curriculum): add context for method chaining and this keyword (#66937)

curriculum/challenges/english/blocks/lecture-working-with-higher-order-functions-and-callbacks/673362cbb475e21eab726506.md

@@ -61,6 +61,38 @@ While method chaining can make code more concise and readable, it's important to
 
 Very long chains can become difficult to debug, as it's not immediately clear which step in the chain might be causing an issue. It's often a good practice to break very long chains into multiple steps for better clarity and easier debugging.
 
+You can also chain methods on an object. In this case, each method returns `this`, which refers to the current object, allowing the next method in the chain to run on it.
+
+:::interactive_editor
+
+```js
+const calculator = {
+  total: 0,
+  add(n) {
+    this.total += n;
+    return this;
+  },
+  multiply(n) {
+    this.total *= n;
+    return this;
+  },
+  subtract(n) {
+    this.total -= n;
+    return this;
+  },
+  getResult() {
+    return this.total;
+  }
+};
+
+const result = calculator.add(5).multiply(2).subtract(3).getResult();
+console.log(result); // 7
+```
+
+:::
+
+This way, each method returns the same object, so you can keep chaining calls one after another.
+
 # --questions--
 
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