Q330- Give the output: console.log(x.init(2).add(4).mul(3).div(2).disp())? What is x?

This question is testing method chaining + object design.

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🔹 Given Code

console.log(
  x.init(2).add(4).mul(3).div(2).disp()
);

To answer this, we must first understand what x is.

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✅ What is x?

x is an object that:

• Stores an internal value
• Each method updates that value
• Each method returns this to allow chaining
• disp() returns the final value

This pattern is called a fluent interface / method chaining.

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✅ Definition of x

const x = {
  value: 0,

  init(n) {
    this.value = n;
    return this;
  },

  add(n) {
    this.value += n;
    return this;
  },

  mul(n) {
    this.value *= n;
    return this;
  },

  div(n) {
    this.value /= n;
    return this;
  },

  disp() {
    return this.value;
  }
};

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🔍 Step-by-Step Evaluation

x.init(2)      // value = 2
 .add(4)       // value = 6
 .mul(3)       // value = 18
 .div(2)       // value = 9
 .disp();      // returns 9

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✅ Final Output

9

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🧠 Why This Works (Important Concept)

• Each method returns this
• this refers to object x

• Enables chaining like:

  x.method1().method2().method3()
  

This is commonly used in:

• jQuery ($('div').addClass().css())
• Lodash / utility libraries
• Builder patterns
• Configuration APIs

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🎯 Short Interview Answer

x is an object implementing method chaining by returning this from each method.
The expression evaluates step by step and finally returns 9.

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⭐ One-line summary

x is a chainable object, and the output is 9.