JavaScript: a highly effective method for verifying if a variable is a function, an array, or an object

Question

JavaScript: a highly effective method for verifying if a variable is a function, an array, or an object

Imagine a scenario where we have a variable that could potentially be a function, object, or array.

I am in search of the most efficient method to determine its type.

In my opinion, the current approach is not optimized because if I already know that isFunction = true, there's no need to calculate the other variables (isArray, isObject);

What would be the best sequence to calculate them in order to optimize resources using ternary operations?

var isFunction,
    isArray,
    isObject;

var obj = function () {};

isFunction = (typeof obj === "function") ? true : false;
isArray = (obj.length > 0) ? true : false;
isObject = (typeof obj === "object") ? true : false;

console.log(isFunction , isArray , isObject ); // true, false, false (the correct way)
console.log(isFunction , isArray , isObject ); // true, undefined, undefined

javascript

Answer 1

Answer №1

This code snippet has been optimized for efficiency without compromising readability. It works well in modern browsers with native support for the some method, which stops executing the callback once a condition is met within an array.

To ensure compatibility with older browsers, it's advised to include Array.prototype.some.

function isOneOf(obj, types) {
  var type;
  type = Object.prototype.toString.call(obj);
  return types.split(' ').some(function (t) {
    return type.indexOf(t) > -1;
  });
}

isOneOf({}, 'Array Object Function');

This function supports various types such as Array, Date, Error, Function, Null, Number, Object, String, and Undefined. Although extensive cross-browser testing has not been conducted, it's advisable to perform thorough unit tests before relying solely on this implementation.

Answer 2

This code snippet has been optimized for efficiency without compromising readability. It works well in modern browsers with native support for the some method, which stops executing the callback once a condition is met within an array.

To ensure compatibility with older browsers, it's advised to include Array.prototype.some.

function isOneOf(obj, types) {
  var type;
  type = Object.prototype.toString.call(obj);
  return types.split(' ').some(function (t) {
    return type.indexOf(t) > -1;
  });
}

isOneOf({}, 'Array Object Function');

This function supports various types such as Array, Date, Error, Function, Null, Number, Object, String, and Undefined. Although extensive cross-browser testing has not been conducted, it's advisable to perform thorough unit tests before relying solely on this implementation.

Answer 3

Answer №2

Here are the various functions from the dojo toolkit used to test for arrays, functions, and more:

checkString = function(str){
    return (typeof str == "string" || str instanceof String); // Returns a Boolean
},

verifyArray = function(arr){
    return arr && (arr instanceof Array || typeof arr == "array"); // Returns a Boolean
},

validateFunction = function(func){
    return opts.call(func) === "[object Function]";
},

determineObject = function(obj){
    return obj !== undefined &&
        (obj === null || typeof obj == "object" || lang.isArray(obj) || lang.isFunction(obj)); // Returns a Boolean
},

confirmArrayLike = function(item){
    return item && item !== undefined &&
        !lang.isString(item) && !lang.isFunction(item) &&
        !(item.tagName && item.tagName.toLowerCase() == 'form') &&
        (lang.isArray(item) || isFinite(item.length));
},

I personally don't see the need to optimize this particular code. If optimization is a concern, it's best to utilize simpler functions without overloading where these checks are not required.

Answer 4

Here are the various functions from the dojo toolkit used to test for arrays, functions, and more:

checkString = function(str){
    return (typeof str == "string" || str instanceof String); // Returns a Boolean
},

verifyArray = function(arr){
    return arr && (arr instanceof Array || typeof arr == "array"); // Returns a Boolean
},

validateFunction = function(func){
    return opts.call(func) === "[object Function]";
},

determineObject = function(obj){
    return obj !== undefined &&
        (obj === null || typeof obj == "object" || lang.isArray(obj) || lang.isFunction(obj)); // Returns a Boolean
},

confirmArrayLike = function(item){
    return item && item !== undefined &&
        !lang.isString(item) && !lang.isFunction(item) &&
        !(item.tagName && item.tagName.toLowerCase() == 'form') &&
        (lang.isArray(item) || isFinite(item.length));
},

I personally don't see the need to optimize this particular code. If optimization is a concern, it's best to utilize simpler functions without overloading where these checks are not required.

JavaScript: a highly effective method for verifying if a variable is a function, an array, or an object

Answer №1

Answer №2

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