javascript - 如何检查json中的值是node js中的字符串还是数组

Question

我在 Node js中有一个像这样的数组Json。

JSON 1

var json1= {
  bookmarkname: 'My Health Circles',
  bookmarkurl: 'http://localhost:3000/',
  bookmark_system_category: [ '22', '1' ]
}

JSON 2

var json2 = {
  bookmarkname: 'My Health Circles',
  bookmarkurl: 'http://localhost:3000/',
  bookmark_system_category:'22'
}

我尝试过:

var length1=json1.bookmark_system_category.length;

var length1=json2.bookmark_system_category.length;

预期输出:

l1=2;
l2=1;

Answer 1

length is property of string as well as array

在第二种情况下，它正在计算字符串的长度，即2

也许你需要一个条件:

var json1 = {
  bookmarkname: 'My Health Circles',
  bookmarkurl: 'http://localhost:3000/',
  bookmark_system_category: ['22', '1']
};
var json2 = {
  bookmarkname: 'My Health Circles',
  bookmarkurl: 'http://localhost:3000/',
  bookmark_system_category: '22'
};

var getLength = function(input) {
  if (typeof input === 'string') {
    return 'Is String';
  } else {
    return input.length;
  }
}

var length1 = getLength(json1.bookmark_system_category);
var length2 = getLength(json2.bookmark_system_category);
alert(length1);
alert(length2)