如何检查 JSON 字符串在 JavaScript 中是否有值？
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How to check if a JSON string has a value in JavaScript?
提问by BalaKrishnan?
Is there is any way to check if the json string has the value(char or string)? Here is the example:
有没有办法检查json字符串是否具有值（字符或字符串）？这是示例：
{
"firstName": "John",
"lastName": "Smith",
"age": 25,
"address": {
"streetAddress": "21 2nd Street",
"city": "New York",
"state": "NY",
"postalCode": 10021
}
}
I have to check if this json has "m". It must know that "m" exists in a value.
我必须检查这个json是否有“m”。它必须知道“m”存在于一个值中。
回答by Moazzam Khan
use this method, if you have json string, you can use json = $.parseJSON(jsonStr)to parse -
使用这个方法，如果你有json字符串，你可以json = $.parseJSON(jsonStr)用来解析——
function checkForValue(json, value) {
for (key in json) {
if (typeof (json[key]) === "object") {
return checkForValue(json[key], value);
} else if (json[key] === value) {
return true;
}
}
return false;
}
回答by djheru
Assuming that the JSON object is assigned to var user
假设将 JSON 对象分配给 var 用户
if(JSON.stringify(user).indexOf('m') > -1){ }
Sorry, upon reading new comments I see you're only looking to see if the string is in a key only. I thought you were looking for an 'm' in the entire JSON (as a string)
抱歉，在阅读新评论时，我发现您只想查看字符串是否仅在键中。我以为你在整个 JSON 中寻找一个“m”（作为一个字符串）
回答by tomaroo
Assuming you get your object syntax corrected, you can loop through the properties in an object by using a forloop:
假设您纠正了对象语法，您可以使用循环遍历对象中的属性for：
for(props in myObj) {
if(myObj[props] === "m") { doSomething(); }
}
回答by eatonphil
Possibly something like this?
可能是这样的？
function parse_json(the_json, char_to_check_for)
{
try {
for (var key in the_json) {
var property = the_json.hasOwnProperty(key);
return parse_json(property);
}
}
catch { // not json
if (the_json.indexof(char_to_check_for) !=== -1)
{
return true;
}
return false;
}
}
if (parse_json(my_json,'m'))
{
alert("m is in my json!");
}
回答by Gibolt
If looking in one layer and not a substring:
如果查看一层而不是子字符串：
const hasValue = Object.values(obj).includes("bar");
If looking in one layer for a substring, and no objects as values:
如果在一层中查找子字符串，并且没有对象作为值：
const hasChar = Object.values(obj).join("").includes("m");
If looking in multi-layer for a substring:
如果在多层中查找子字符串：
const list = Object.values(a);
for (let i = 0; i < list.length; i++) {
const object = list[i];
if (typeof object === "object") {
list.splice(i, 1); // Remove object from array
list = list.concat(Object.values(object)); // Add contents to array
}
}
// It is important to join by character not in the search substring
const hasValue = list.join("_").includes("m");
NOTE: If searching for a key instead, check this post
注意：如果要搜索密钥，请查看此帖子
