What is the difference between call( ) and apply( )?

JavaScriptPegasystems

call( ) vs apply( )

Both call( ) and apply( ) are methods that allow you to execute a function with a specified 'this' context and arguments. They enable you to control what the 'this' keyword refers to inside the function being called.

Here's an example to demonstrate this:

const person = {
  name: 'John',
  greet: function () {
    return `Hello, ${this.name}`;
  },
};

const manager = {
  name: 'Sarah',
};

// Using the greet function with manager's context
person.greet.call(manager); // Returns: "Hello, Sarah"
person.greet.apply(manager); // Returns: "Hello, Sarah"

The difference between call and apply

The main difference between call() and apply() is how they handle the arguments:

  • call( ) accepts arguments individually, functionName.call(thisContext, arg1, arg2).
  • apply( ) accepts arguments as an array, functionName.apply(thisContext, [arg1, arg2]).
const person = {
  name: 'John',
  introduce: function (role, department) {
    return `Hello, I'm ${this.name}, ${role} in ${department}`;
  },
};

const employee = {
  name: 'Sarah',
};

// Using call() - arguments are passed individually
person.introduce.call(employee, 'Manager', 'Sales');
// Returns: "Hello, I'm Sarah, Manager in Sales"

// Using apply() - arguments are passed as an array
person.introduce.apply(employee, ['Manager', 'Sales']);
// Returns: "Hello, I'm Sarah, Manager in Sales"

Both methods achieve the same outcome, with the choice between them typically depending on whether your arguments are available as separate values or as an array.

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