为什么我无法在json数据上调用.get /如何将json转换为地图

Question

I'm trying to write a test for a function which takes a map as a parameter,

When the code runs normally outside of a test the parameter can take the form (when I call toString):

Map { "id": "jobs", "label": "Jobs", "nodeType": "ROOT", "childNodesURI": "jobs?owner=*", "childIds": List [], "isFetchingChildren": false, "isToggled": true, "jobName": "" }

var node = {
                id: "jobs", 
                label: "JES Jobs", 
                nodeType: "ROOT", 
                childNodesURI: "jobs?owner=*", 
                childIds: [],
                isFetchingChildren: false, 
                isToggled: true, 
                jobName: "" };
                console.log(node.get("id"));

When node.get("id") is called I get "TypeError: node.get is not a function"

I'm assuming this is because there's no function .get() foo a JSON object but not truly sure... If this is the case, how do I convert or initialise the JSON as a map?

Answer 1

What you are showing us is a javascript object. If you need to call a "key" in this case you should use theObject.theProperty like below

 var node = { id: "jobs", label: "JES Jobs", nodeType: "ROOT", childNodesURI: "jobs?owner=*", childIds: [], isFetchingChildren: false, isToggled: true, jobName: "" }; //Call the object property ID console.log(node.id); 

If you need a map you need to it this way :

 var myMap = new Map(); // setting the values myMap.set("id", "jobs"); console.log(myMap.get("id")); 

If you want to create your map starting from your object you can do it like this

 var node = { id: "jobs", label: "JES Jobs", nodeType: "ROOT", childNodesURI: "jobs?owner=*", childIds: [], isFetchingChildren: false, isToggled: true, jobName: "" }; function buildMap(obj) { let map = new Map(); Object.keys(obj).forEach(key => { map.set(key, obj[key]); }); return map; } const map = buildMap(node); console.log(map.get("id")); 

Answer 2

You can just access node.id using the code you have. There is no get() method on an object literal unless you extend the prototype yourself.

Map should accept an iterable object as a parameter when you create one according to the docs. However in practice I find this generates an undefined is not a function error when using an object instead of an array. Also looking at the docs, the browser support is not complete ( https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Map ).

For example (quoted from above link):

[1] Starting with Chrome 31, the feature was available behind a preference. In chrome://flags, activate the entry “Enable Experimental JavaScript”.

Your options as I see them are; you can iterate over your JSON

var m = new Map();
var json = {'foo': 'bar'};

for(var i in json) {
    m.set(i, json[i]);
}
m.get('foo');

Or if you don't really need the Map methods stick with the object literal.

json.foo;