我如何找到 'abc' 在数组中 [{title:'ccc'},{title:'abc'}

Question

我想知道 [{title:'ccc'},{title:'abc'},{title:'ddd'}] 中是否有“abc”let a = 'abc'let b = [{title:'ccc'},{title:'abc'},{title:'ddd'}]if there is a in b{   return 'yes'} else {   return 'no}//我该怎么做以及如何判断

Answer 1

最简单的答案是some：

let a = 'abc'

let b = [{title:'ccc'},{title:'abc'},{title:'ddd'}];

let aInB = b.some(({ title }) => title == a);

console.log(aInB);

您还可以includes与flatMap和一起使用Object.values：

let a = 'abc'

let b = [{title:'ccc'},{title:'abc'},{title:'ddd'}];

let aInB = b.flatMap(Object.values).includes(a) ? "Yes" : "No"; 

console.log(aInB);

没有flatMap或的版本flat（不受支持）：

let a = 'abc'

let b = [{title:'ccc'},{title:'abc'},{title:'ddd'}];

let aInB = b.map(Object.values).reduce((a, c) => a.concat(c)).includes(a) ? "Yes" : "No"; 

console.log(aInB);

ES5 语法：

var a = 'abc'

var b = [{title:'ccc'},{title:'abc'},{title:'ddd'}];

var aInB = b.map(function(e) {

  return Object.keys(e).map(function(key) {

    return e[key];

  });

}).reduce(function(a, c) {

  return a.concat(c);

}).indexOf(a) > -1 ? "Yes" : "No";

console.log(aInB);

Answer 2

您可以使用Array#find。

Array#find将返回匹配项，或者undefined如果没有找到匹配项，则您可以在if语句中使用结果。

let a = 'abc'

let b = [{title:'ccc'},{title:'abc'},{title:'ddd'}]

let c = b.find((d) => d.title === a);

if (c) {

    return 'yes';

} else {

    return 'no';

}