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Assume I have an indexed array of objects, such as these containing lines of a popular folk song ;)
var lyrics = [
{line : 2, words : "He's a lumberjack and he's okay"},
{line : 1, words : "I'm a lumberjack and I'm okay"},
{line : 3, words : "He sleeps all night and he works all day"}
];
My comparator will display the objects in the view according to each object's index. I want to be able to perform the three tasks on this array:
Task 1) Reindex on drag 'n drop
Re-arrange the order of the objects via drag and drop. Assume I already know how to implement drag and drop. Task example: Drag "He's a lumberjack and he's okay" from index "1" to after "I'm a lumberjack and I'm okay". "He's a lumberjack and he's okay" should now occupy index "2" and "I'm a lumberjack and I'm okay" should occupy index "1". The resulting array should be:
var lyrics = [
{line : 1, words : "I'm a lumberjack and I'm okay"},
{line : 2, words : "He's a lumberjack and he's okay"},
{line : 3, words : "He sleeps all night and he works all day"}
];
Task 2) Re-index on insert
Add an object to any point in the array, reindexing all the items in the array. Task example: Add a "I sleep all night and I work all day" object as the second item in the array. The resulting array should be:
var lyrics = [
{line : 1, words : "I'm a lumberjack and I'm okay"},
{line : 2, words : "I sleep all night and I work all day"},
{line : 3, words : "He's a lumberjack and he's okay"},
{line : 4, words : "He sleeps all night and he works all day"}
];
Task 3) Re-index on delete
Delete an object from an array and reindex all the items in the array. So for example, if object with index "3" were deleted, the resulting array should be:
var lyrics = [
{line : 1, words : "I'm a lumberjack and I'm okay"},
{line : 2, words : "I sleep all night and I work all day"},
{line : 3, words : "He sleeps all night and he works all day"}
];
I don't have a CS degree so I'm kind of stumped on what algorithm would help me handle this. Can someone point me in the right direction?
I'm working with javascript, so if anyone knows anything that does the above, I'm all ears.
681
To change the position of an element in an array:Use the splice() method to insert the element at the new index in the array. The splice method changes the original array by removing or replacing existing elements, or adding new elements at a specific index.
We can reorder the elements in the array by using the following methods. One of the ways to achieve the above task is b using sort() method. The sort() is an in-built method in JavaScript, which sorts the alphabetic elements. By default, it sorts in ascending order.
Can we change the starting index of an array from 0 to 1 in any way? Explanation: No. You can not change the C Basic rules of Zero Starting Index of an Array.
Changing the element of an array To change the value of a specific element of an array, we refer to its index number or position in the given array. Remember that in C++, the first character or element of a given object has its index position or number as 0 .
I would totally simplify your entire structure:
Use a native javascript array, instead of storing an extra key (line) use the javascript index as the key, which means javascript (if used properly) will manage it for you, and use less memory.
So we've got an array of strings:
var f = [];
f.push('first');
f.push('third');
f.push('fourth');
// reindex on insert
// lets insert second in the natural place
f.splice(1,0,'second'); // ["first", "second", "third", "fourth"]
// reindex on delete
// lets delete 'third'
f.splice(2,1); // ["first", "second", "fourth"]
etc.
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