Lodash - 如何總結陣列

Question

的數組的長度我有陣

const myArrays = [ 
    [ 1, 2, 3, 4], // length = 4 
    [ 1, 2], // length = 2 
    [ 1, 2, 3], // length = 3 
]; 

數組我如何讓所有的孩子陣列的總和長度是多少？

const length = 4 + 2 + 3 

Answer 1

您可以使用_.sumBy

const myArrays = [ 
 
    [ 1, 2, 3, 4], // length = 4 
 
    [ 1, 2], // length = 2 
 
    [ 1, 2, 3], // length = 3 
 
]; 
 

 
var length = _.sumBy(myArrays, 'length'); 
 
console.log("length =", length);

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Answer 2

您可以使用_.forEach或_.reduce

const myArrays = [ 
 
    [ 1, 2, 3, 4], // length = 4 
 
    [ 1, 2], // length = 2 
 
    [ 1, 2, 3], // length = 3 
 
]; 
 

 
var length = 0; 
 

 
_.forEach(myArrays, (arr) => length += arr.length); 
 

 
console.log('Sum of length of inner array using forEach : ', length); 
 

 
length = _.reduce(myArrays, (len, arr) => { 
 
    len += arr.length; 
 
    return len; 
 
}, 0); 
 

 
console.log('Sum of length of inner array using reduce : ', length);

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