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集体记忆
lodash.js->Array->difference
用法
返回一个去重后的数组,每个值不蕴含在其余数组参数中。后果值的程序是由第一个数组中的程序确定。
例子
_.difference([1,2,3],[3],[1,5])
//==>[2];
源码了解
difference(array, values, iteratee, comparator) {
var index = -1,
includes = arrayIncludes,
isCommon = true,
length = array.length,
result = [],
valuesLength = values.length;
if (!length) {return result;}
if (iteratee) {values = arrayMap(values, baseUnary(iteratee));
}
if (comparator) {
includes = arrayIncludesWith;
isCommon = false;
}
else if (values.length >= LARGE_ARRAY_SIZE) {
includes = cacheHas;
isCommon = false;
values = new SetCache(values);
}
outer:
while (++index < length) {var value = array[index],
computed = iteratee ? iteratee(value) : value;
if (isCommon && computed === computed) {
var valuesIndex = valuesLength;
while (valuesIndex--) {if (values[valuesIndex] === computed) {continue outer;}
}
result.push(value);
}
else if (!includes(values, computed, comparator)) {result.push(value);
}
}
return result;
}
1. 外围代码
outer:
while (++index < length) {var value = array[index],
computed = iteratee ? iteratee(value) : value;
if (isCommon && computed === computed) {
var valuesIndex = valuesLength;
while (valuesIndex--) {if (values[valuesIndex] === computed) {continue outer;}
}
result.push(value);
}
else if (!includes(values, computed, comparator)) {result.push(value);
}
}
return result;
` 思路:` 将除 array 之外的数组参数合并去重,失去 values, 再应用 includes 办法,判断 array 中的元素是否存在于 values 中,若不存在行将 value 放进新数组 result 中,最初返回 result。
延申
假如有一需要,重点展现本月在本年没有呈现过的新呈现的天气类型:
difference(month12,month1,month2.....);
正文完
发表至: javascript
2020-12-04