zyAdmin/node_modules/clonedeep/index.js

'use strict';

// Method that will return the data type for any structure passed to it
function getDataType (data) {
    // Use the objects toString method on the data.
    // This will return something like [object String]
    // Then we use .slice to grab the last portion of it (in this case the "string" bit)
    return Object.prototype.toString.call(data).slice(8, -1);
}

// Create a method to detect whether an object contains a circular reference
function isCyclic (data) {
    
    // Create an array that will store the nodes of the array that have already been iterated over
    let seenObjects = [];

    function detect (data) {
        // If the data pass is an object
        if (data && getDataType(data) === "Object") {
            
            // If the data is already in the seen nodes array then we know there is a circular reference
            // Therefore return true
            if (seenObjects.indexOf(data) !== -1) {
                return true;
            }

            // Add the data to the seen objects array
            seenObjects.push(data);

            // Begin iterating through the data passed to the method
            for (var key in data) {
                // Recall this method with the objects key
                if (data.hasOwnProperty(key) === true && detect(data[key])) {
                    return true;
                }
            }
        }
        return false;
    }

    // Return the method
    return detect(data);
}

const deepClone = function (data) {
    // If the data is null or undefined then we return undefined
    if (data === null || data === undefined) {
        return undefined;
    }

    // Get the data type and store it
    const dataType = getDataType(data);

    // If the data passed is a date object
    if (dataType === "Date") {
        // Create a new date object and set the time to what it was previously
        let clonedDate = new Date();
        clonedDate.setTime(data.getTime());

        return clonedDate;
    }

    // If the data passed is an object
    if (dataType === "Object") {
        // Check for circular references, if there are then we just return the un-cloned data.
        if (isCyclic(data) === true) {
            return data;
        }

        // Create a new object that will store our copied data
        let copiedObject = {};

        // Iterate over the objects keys
        for (let key in data) {
            // Clone the keys of each of the objects so that we can deeply copy and nested data structures
            // For example if an object has a key value that is an array
            // Add this cloned key value to the copiedObject we created earlier
            copiedObject[key] = deepClone(data[key]);
        }

        // Return the deeply copied object
        return copiedObject;
    }

    // If the data is an array
    if (dataType === "Array") {
        // Create a new array that will have no references to the one we want to copy
        let copiedArray = [];

        // Iterate over the arrays elements
        for (var i = 0; i < data.length; i++) {
            // Push the arrays elements to this new array
            // First recall this method with the elements
            // This is so arrays of objects and other nested data structures get correctly cloned.
            copiedArray.push(deepClone(data[i]));
        }

        // Return the cloned array
        return copiedArray;
    }

    // If it's any other data type like a string or number, they don't need cloning so we just return them
    else {
        return data;
    }
}

// Export a new instance of the clone constructor
module.exports = deepClone;