在JavaScript中访问array.map中以前迭代的元素？
假设以下是我们的数组-
var details = [
{subjectId:110, subjectName: 'Java' },
{subjectId:111, subjectName: 'Javascript' },
{subjectId:112, subjectName: 'MySQL' },
{subjectId:113, subjectName: 'MongoDB' }
];现在，使用的概念map()。代码如下-
示例
var details = [
{subjectId:110, subjectName: 'Java' },
{subjectId:111, subjectName: 'JavaScript' },
{subjectId:112, subjectName: 'MySQL' },
{subjectId:113, subjectName: 'MongoDB' }
];
var output = details.map((detailsObject, index) =>
{
var tempObject = {};
tempObject.subjectId= detailsObject.subjectId;
tempObject.subjectName = detailsObject.subjectName;
const getThePreviousObject = index != 0 ? details[index-1] : null;
tempObject.previousSubjectName = getThePreviousObject ?
getThePreviousObject.subjectName : 'Not Available'
return tempObject;
})
console.log(output);要运行上述程序，您需要使用以下命令-
node fileName.js.
在这里，我的文件名为demo204.js。
输出结果
这将产生以下输出-
PS C:\Users\Amit\javascript-code> node demo204.js
[
{
subjectId: 110,
subjectName: 'Java',
previousSubjectName: 'Not Available'
},
{
subjectId: 111,
subjectName: 'JavaScript',
previousSubjectName: 'Java'
},
{
subjectId: 112,
subjectName: 'MySQL',
previousSubjectName: 'JavaScript'
},
{
subjectId: 113,
subjectName: 'MongoDB',
previousSubjectName: 'MySQL'
}
]