我想b一定是这样的标签：

let b = ['pending', 'answer', 'reject']

我们可以用c和这个代码：

var a = { pending: '500', answer: '200', reject: '400' }
var b =['pending', 'answer',  'reject']

let c =[]

for (let i = 0; i<b.length; i++) {
  c.push({status: a[b[i]], title:b[i]})
}

console.log(c)

你似乎不需要 b 为了这个
最简单的可能是

var a = { pending: '500', answer: '200', reject: '400' }
var c = Object.entries(a).map(([title, status]) => ({status: +status, title}))
console.log(c);