如何从嵌套对象获取键值

Question

I am having below object where I am trying to get all the id values.

[{
    "type": "test",
    "id": "100",
    "values": {
        "name": "Alpha"
    },
    "validations": []
}, {
    "type": "services",
    "validations": [{
        "id": "200",
        "name": "John",
        "selection": [{
            "id": "300",
            "values": {
                "name": "Blob"
            }
        }]
    }]
}]

Using the below code, I am getting only the first id value. Is there any way to get all the id values from the nested object without using any external module.

for (var prop in obj) {
            console.log(prop)
            if (prop === key) {
                set.push(prop);
            }
        }

Expected Output

[100,200,300]     //all id values

Answer 1

You can use a JavaScript function like below to get the nested properties:

function findProp(obj, key, out) {
    var i,
        proto = Object.prototype,
        ts = proto.toString,
        hasOwn = proto.hasOwnProperty.bind(obj);

    if ('[object Array]' !== ts.call(out)) out = [];

    for (i in obj) {
        if (hasOwn(i)) {
            if (i === key) {
                out.push(obj[i]);
            } else if ('[object Array]' === ts.call(obj[i]) || '[object Object]' === ts.call(obj[i])) {
                findProp(obj[i], key, out);
            }
        }
    }

    return out;
}

Check this Fiddle for a working solution.

Answer 2

Using Object.keys

 function findProp(obj, prop) { var result = []; function recursivelyFindProp(o, keyToBeFound) { Object.keys(o).forEach(function (key) { if (typeof o[key] === 'object') { recursivelyFindProp(o[key], keyToBeFound); } else { if (key === keyToBeFound) result.push(o[key]); } }); } recursivelyFindProp(obj, prop); return result; } // Testing: var arr = [{ "type": "test", "id": "100", "values": { "name": "Alpha" }, "validations": [] }, { "type": "services", "validations": [{ "id": "200", "name": "John", "selection": [{ "id": "300", "values": { "name": "Blob" } }] }] }]; console.log(findProp(arr, "id")); 

Answer 3

To get the keys from nested objects, you first need to put your code in a function, then for each of the top-level keys, check if it's an array or object. If it is, just call your function again from within that function (weird, I know.) Just make sure you don't skip the check of whether it's an object. You'll get stuck in an infinite loop. Something like this:

function parseObjectKeys(obj) {
  for (var prop in obj) {
    console.log(prop)
    var sub = obj[prop]
    if (typeof(sub) == "object") {
      parseObjectKeys(sub);
    }
  }
}

Here's a more complex example: https://jsfiddle.net/tfqLnzLm/1/

Answer 4

You can use a XPath styled json parser like JSONPath . The version I'm presenting here is a extended version I did here :

 function jsonPath(obj,expr,arg){var P={resultType:arg&&arg.resultType||"VALUE",result:[],normalize:function(e){var t=[];return e.replace(/[\\['](\\??\\(.*?\\))[\\]']/g,function(e,r){return"[#"+(t.push(r)-1)+"]"}).replace(/'?\\.'?|\\['?/g,";").replace(/;;;|;;/g,";..;").replace(/;$|'?\\]|'$/g,"").replace(/#([0-9]+)/g,function(e,r){return t[r]})},asPath:function(e){for(var t=e.split(";"),r="$",a=1,n=t.length;n>a;a++)r+=/^[0-9*]+$/.test(t[a])?"["+t[a]+"]":"['"+t[a]+"']";return r},store:function(e,t){return e&&(P.result[P.result.length]="PATH"==P.resultType?P.asPath(e):t),!!e},trace:function(e,t,r){if(e){var a=e.split(";"),n=a.shift();if(a=a.join(";"),t&&t.hasOwnProperty(n))P.trace(a,t[n],r+";"+n);else if("*"===n)P.walk(n,a,t,r,function(e,t,r,a,n){P.trace(e+";"+r,a,n)});else if(".."===n)P.trace(a,t,r),P.walk(n,a,t,r,function(e,t,r,a,n){"object"==typeof a[e]&&P.trace("..;"+r,a[e],n+";"+e)});else if(/,/.test(n))for(var l=n.split(/'?,'?/),s=0,c=l.length;c>s;s++)P.trace(l[s]+";"+a,t,r);else/^\\(.*?\\)$/.test(n)?P.trace(P.eval(n,t,r.substr(r.lastIndexOf(";")+1))+";"+a,t,r):/^\\?\\(.*?\\)$/.test(n)?P.walk(n,a,t,r,function(e,t,r,a,n){P.eval(t.replace(/^\\?\\((.*?)\\)$/,"$1"),a[e],e)&&P.trace(e+";"+r,a,n)}):/^(-?[0-9]*):(-?[0-9]*):?([0-9]*)$/.test(n)&&P.slice(n,a,t,r)}else P.store(r,t)},walk:function(e,t,r,a,n){if(r instanceof Array)for(var l=0,s=r.length;s>l;l++)l in r&&n(l,e,t,r,a);else if("object"==typeof r)for(var c in r)r.hasOwnProperty(c)&&n(c,e,t,r,a)},slice:function(e,t,r,a){if(r instanceof Array){var n=r.length,l=0,s=n,c=1;e.replace(/^(-?[0-9]*):(-?[0-9]*):?(-?[0-9]*)$/g,function(e,t,r,a){l=parseInt(t||l),s=parseInt(r||s),c=parseInt(a||c)}),l=0>l?Math.max(0,l+n):Math.min(n,l),s=0>s?Math.max(0,s+n):Math.min(n,s);for(var o=l;s>o;o+=c)P.trace(o+";"+t,r,a)}},eval:function(x,_v,_vname){try{return $&&_v&&eval(x.replace(/@/g,"_v"))}catch(e){throw new SyntaxError("jsonPath: "+e.message+": "+x.replace(/@/g,"_v").replace(/\\^/g,"_a"))}}},$=obj;return expr&&obj&&("VALUE"==P.resultType||"PATH"==P.resultType)?(P.trace(P.normalize(expr).replace(/^\\$;/,""),obj,"$"),P.result.length?P.result:!1):void 0} // some extensions I have added to JSONPath var jsonPathStore = function(obj,path,values) { var maps=jsonPath(obj, path,{resultType:"PATH"}) maps.map(function(item,index) { return eval( '(' + item.replace(/\\$/,"obj") + '="' + values[index] +'"' + ')' ); }) } var jsonPathDelete = function(obj,path) { var maps=jsonPath(obj, path,{resultType:"PATH"}) maps.map(function(item,index) { return eval( '(' + 'delete ' + item.replace(/\\$/,"obj") + ')' ); }) } var jsonPathRead = function(obj,path) { var maps=jsonPath(obj, path,{resultType:"PATH"}) return maps.map(function(item,index) { return eval( '(' + item.replace(/\\$/,"obj") + ')' ); }) } var jsonObject = [{ "type": "test", "id": "100", "values": { "name": "Alpha" }, "validations": [] }, { "type": "services", "validations": [{ "id": "200", "name": "John", "selection": [{ "id": "300", "values": { "name": "Blob" } }] }] }] // this XPath will read all the id properties starting from the root element console.log( "jsonPathRead All Ids" + JSON.stringify(jsonPathRead(jsonObject,"$..id"), null, 2) ) 

Answer 5

function getIds(obj) {
  for (var x in obj) {
    if (typeof obj[x] === 'object') {
      getIds(obj[x]);
    } else if (x === 'id') {
      console.log(obj.id);
    }
  }
}