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'use strict';
var typeOf = require('kind-of');
/**
* Basic sort algorithm that has similar behavior to `Array.prototype.sort`
* for null and undefined, but also allows sorting by an object property.
*
* @param {Mixed} `a` First value to compare.
* @param {Mixed} `b` Second value to compare.
* @param {String} `prop` Optional property to use when comparing objects. If specified must be a string.
* @return {Number} Returns 1 when `a` should come after `b`, -1 when `a` should come before `b`, and 0 when `a` and `b` are equal.
* @api public
*/
module.exports = function defaultCompare(a, b, prop) {
if (prop != null && typeOf(prop) !== 'string') {
throw new TypeError('expected "prop" to be undefined or a string');
}
var typeA = typeOf(a);
var typeB = typeOf(b);
if (prop) {
if (typeA === 'object') {
a = a[prop];
typeA = typeOf(a);
}
if (typeB === 'object') {
b = b[prop];
typeB = typeOf(b);
}
}
if (typeA === 'null') {
return typeB === 'null' ? 0 : (typeB === 'undefined' ? -1 : 1);
} else if (typeA === 'undefined') {
return typeB === 'null' ? 1 : (typeB === 'undefined' ? 0 : 1);
} else if (typeB === 'null' || typeB === 'undefined') {
return -1;
} else {
return a < b ? -1 : (a > b ? 1 : 0);
}
};