43 lines
1.5 KiB
JavaScript
43 lines
1.5 KiB
JavaScript
|
"use strict";
|
||
|
|
|
||
|
|
var BinarySearch = {
|
||
|
|
/**
|
||
|
|
* Searches for an item in an array which matches a certain condition.
|
||
|
|
* This requires the condition to only match one item in the array,
|
||
|
|
* and for the array to be ordered.
|
||
|
|
*
|
||
|
|
* @param {Array} list The array to search.
|
||
|
|
* @param {Function} comparisonFunction
|
||
|
|
* Called and provided a candidate item as the first argument.
|
||
|
|
* Should return:
|
||
|
|
* > -1 if the item should be located at a lower index than the provided item.
|
||
|
|
* > 1 if the item should be located at a higher index than the provided item.
|
||
|
|
* > 0 if the item is the item you're looking for.
|
||
|
|
*
|
||
|
|
* @return {*} The object if it is found or null otherwise.
|
||
|
|
*/
|
||
|
|
search: function search(list, comparisonFunction) {
|
||
|
|
var minIndex = 0;
|
||
|
|
var maxIndex = list.length - 1;
|
||
|
|
var currentIndex = null;
|
||
|
|
var currentElement = null;
|
||
|
|
|
||
|
|
while (minIndex <= maxIndex) {
|
||
|
|
currentIndex = (minIndex + maxIndex) / 2 | 0;
|
||
|
|
currentElement = list[currentIndex];
|
||
|
|
|
||
|
|
var comparisonResult = comparisonFunction(currentElement);
|
||
|
|
if (comparisonResult > 0) {
|
||
|
|
minIndex = currentIndex + 1;
|
||
|
|
} else if (comparisonResult < 0) {
|
||
|
|
maxIndex = currentIndex - 1;
|
||
|
|
} else {
|
||
|
|
return currentElement;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return null;
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
module.exports = BinarySearch;
|