JavaScript: Create a function that invokes the method at a given key of an object

JavaScript fundamental (ES6 Syntax): Exercise-60 with Solution

Invoke Object Method by Key

Write a JavaScript program to create a function that invokes the method at a given key of an object. Optionally, add any parameters that are supplied to the beginning of the arguments.

• Return a function that uses Function.prototype.apply() to bind context[fn] to context.
• Use the spread operator (...) to prepend any additional supplied parameters to the arguments.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define a function 'bindKey' to bind a method of an object to that object.
const bindKey = (context, fn, ...args) =>
  // Return a new function that applies the specified method of the context with the provided arguments.
  function() {
    return context[fn].apply(context, args.concat(...arguments));
  };

// Define an object 'freddy' with a 'user' property and a 'greet' method.
const freddy = {
  user: 'fred',
  greet: function(greeting, punctuation) {
    return greeting + ' ' + this.user + punctuation;
  }
};

// Bind the 'greet' method of the 'freddy' object.
const freddyBound = bindKey(freddy, 'greet');

// Call the bound method with additional arguments.
console.log(freddyBound('hi', '!')); // Output: "hi fred!"

Output:

hi fred!

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-60-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that takes an object and a method key, then invokes the method with supplied parameters.
• Write a JavaScript function that checks if a given key in an object is a function before calling it with arguments.
• Write a JavaScript program that dynamically calls an object's method by key, using optional parameter injection.

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