如何找到与Javascript具有一定值的数组的所有索引?

Question

在下面的示例代码中，我如何在日期中找到年份为2021的任何数组的所有索引?谢谢你的任何指导!

function test() {
const dates = [
'October 31, 2020',
'November 30, 2020',
'December 31, 2020',
'January 31, 2021',
'February 28, 2021',
'March 31, 2021',
];

// How should the following code be changed to get indexes of any array of year 2021, which should be 3,4,5?
// The following code returned only the first array index, 3, not 3,4,5.
var indexes = dates.findIndex(el => el.includes('2021'));
console.log(indexes);
}

Answer 1

使用

/*<ignore>*/console.config({maximize:true,timeStamps:false,autoScroll:false});/*</ignore>*/
function test() {
const dates = [
'October 31, 2020',
'November 30, 2020',
'December 31, 2020',
'January 31, 2021',
'February 28, 2021',
'March 31, 2021',
];

// The following code returned 3,4,5.
var indexes = dates.reduce((acc,el,i) => el.includes('2021') ? [...acc,i] : acc,[]);
console.log(indexes);
}
test()

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