I need to convert a hash map
{
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
}
to
[
{ "type" : "fruit" , "name" : ["mango","orange"] } ,
{ "type" : "veg" , "name" : ["carrot"] }
]
how do I do that??
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I would like to know how to do it both ways..Sam– Sam2012-04-26 15:44:53 +00:00Commented Apr 26, 2012 at 15:44
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please, remember to always provide some code identation, it makes the question easier to readFabrizio Calderan– Fabrizio Calderan2012-04-26 15:45:34 +00:00Commented Apr 26, 2012 at 15:45
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thanks for the edit...will remember it nxt time..Sam– Sam2012-04-26 15:47:04 +00:00Commented Apr 26, 2012 at 15:47
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2Note that JavaScript has no "hash map", just "objects".maerics– maerics2012-04-26 16:10:08 +00:00Commented Apr 26, 2012 at 16:10
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8 Answers
You can do it like this (in a working snippet):
var input = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
}
var output = [], item;
for (var type in input) {
item = {};
item.type = type;
item.name = input[type];
output.push(item);
}
// display result
document.write(JSON.stringify(output));Or, if you or someone else has been extending the Object prototype with enumerable properties (which I think is a bad practice personally), then you could use this to protect from that:
var input = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
}
var output = [], item;
for (var type in input) {
if (input.hasOwnProperty(type)) {
item = {};
item.type = type;
item.name = input[type];
output.push(item);
}
}
// display result
document.write(JSON.stringify(output));And, using some more modern functionality:
var input = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
};
var output = Object.keys(input).map(function(key) {
return {type: key, name: input[key]};
});
// display the result
document.write(JSON.stringify(output));9 Comments
gen_Eric
I suggest checking
hasOwnProperty inside the for...in loop.
Anurag Uniyal
@Rocket I do NOT suggest checking hasOwnProperty inside the for...in loop.
gen_Eric
@AnuragUniyal: Please explain why.
jfriend00
I gave the OP either option in my answer (with or without
hasOwnProperty()). I don't personally allow extension of Object in my pages so I don't have to add extra code to protect from it. If I was in an environment where that was a possibility, I would code to protect from it. |
In a browser that supports ES5 – or where you added a shim for it:
var stuff = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
}
var array = Object.keys(stuff).map(function(key) {
return {"type" : key, "name" : stuff[key] }
})
See: Object.keys, Array's map
Or, in the old fashion way:
var stuff = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
}
var array = []
for (var key in stuff) {
if (stuff.hasOwnProperty(key)) {
array.push({"type" : key, "name" : stuff[key] })
}
}
Please notice that in both cases the array's value are shared because in JS the objects are passed by reference. So, for instance, stuff["fruit"] and array[0].name points to the same reference of the array ["mango", "orange"]. It means, if you change one of them, the other will be changed as well:
stuff["fruit"].push("apple");
alert(array[0].name); // "mango", "orange", "apple"
To avoid that, you can use slice to have a one-level deep copy of your array. So in the code above, instead of:
"name" : stuff[key]
you will have:
"name" : stuff[key].slice(0)
Hope it helps.
Comments
For those using ES6 maps...
Assuming you have...
const m = new Map()
m.set("fruit",["mango","orange"]);
m.set("veg",["carrot"]);
You can use...
const arr = Array.from(map, ([key, val]) => {
return {type: key, name: val};
});
Note that Array.from takes iterables as well as array-like objects.
Comments
I would like to give an "oneline" solution:
var b = Object.keys(a).map(e => { return { type:e, name:a[e] } });
Economy of words at your service. Question asked for translating an object to an array, so I'm not duplicating above answer, isn't it?
Comments
It looks simple, key of your map is type and values are name, so just loop thru map and insert object in a list e.g.
var d = { "fruit" : ["mango","orange"],"veg" :["carrot"]}
var l = []
for(var type in d){
l.push({'type':type, 'name': d[type]})
}
console.log(l)
output:
[{"type":"fruit","name":["mango","orange"]},{"type":"veg","name":["carrot"]}]
35 Comments
Fabrizio Calderan
as a good practice it's better to also use
.hasOwnProperty() methodAnurag Uniyal
@F.Calderan why that is necessary in this case, when format is fixed map?
Fabrizio Calderan
I didn't say it's necessary but we can't say if that object has some other properties added via
Object.prototypeAnurag Uniyal
@Rocket if somebody can modify object without me knowing then he can change e.g.
Array.prototype.join = function(){alert("hacked!")} now will you say I should be using any array methods at all |
Not exactly the answer you are looking for, but it could be useful for general purpose.
var hash2Array = function(hash, valueOnly) {
return Object.keys(hash).map(function(k) {
if (valueOnly) {
return hash[k];
} else {
var obj={};
obj[k] = hash[k];
return obj;
}
});
};
//output
hash2Array({a:1, b:2}); // [{a:1}, {b:2}]
hash2Array({a:1, b:2},true) // [1,2]
Comments
In case of using underscore.js:
var original = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
}
var converted = _.map(original, function(name, type){
return {
type: type,
name: name
};
});
Comments
No Need of loop
var a = {
"fruit" : ["mango","orange"],
"veg" : ["carrot"]
};
var b = [
{ "type" : "fruit" , "pop" : function(){this.name = a[this.type]; delete this.pop; return this} }.pop() ,
{ "type" : "veg" , "pop" : function(){this.name = a[this.type]; delete this.pop; return this} }.pop()
]
1 Comment
drzaus
that's...bizarre. at least reuse the function ;)