reduce用法reduce...to 和reduce...by有啥区别

几个关于js数组方法reduce的经典片段

reduce方法有两个参数，第一个参数是一个callback，用于针对数组项的操作；第二个参数则是传入的初始值，这个初始值用于单个数组项的操作。

需要注意的是，reduce方法返回值并不是数组，而是形如初始值的经过叠加处理后的操作。

reduce方法最常见的场景就是叠加。

var items = [10, 120, 1000]; // our reducer function var reducer = function add(sumSoFar, item) { return sumSoFar + item; }; // do the job var total = items.reduce(reducer, 0); console.log(total); // 1130

python map和reduce的用法

map(function, sequence[, sequence, ...]) -> list Return a list of the results of applying the function to the items of the argument sequence(s). If more than one sequence is given, the function is called with an argument list consisting of the corresponding item of each sequence, substituting None for missing values when not all sequences have the same length. If the function is None, return a list of the items of the sequence (or a list of tuples if more than one sequence). reduce(...) reduce(function, sequence[, initial]) -> value Apply a function of two arguments cumulatively to the items of a sequence, from left to right, so as to reduce the sequence to a single value. For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates ((((1+2)+3)+4)+5). If initial is present, it is placed before the items of the sequence in the calculation, and serves as a default when the sequence is empty.

reduce...to 和reduce...by有啥区别

reduce to、reduce by这两个短语都表示“减少”，其区别是： 1、前者用于表示减少的程度。

pany?must?reduce?costs?pete?effectively.? 公司要有效地参与竞争必须降低成本。

2、后者用于表示减少的数量。

Tests?indicate?this?might?reduce?activity?by?a?factor?between?10?an?100.? 测试结果表明，这可将放射性降低到原来的1/10-1/100。

扩展资料 词语用法： 1、reduce的基本意思是“减少”，指重量、程度、数目、范围、速度等减少或降低，不仅可以指量的变化，还可以指质的转变。

2、reduce引申可作“降职”“使…陷入某种状态或状况中”“将…概括或简化”“将…还原”“征服”“攻陷”等解。

3、reduce可用作及物动词，也可用作不及物动词。

用作及物动词时接名词或代词作宾语。

可用于被动结构。

4、reduce偶尔也可接动词不定式作宾语补足语，意思是“使…不得不…”。