问题
I have an array of objects with duplicates and I'm trying to get a unique listing, where uniqueness is defined by a subset of the properties of the object. For example,
Current JSON Object:
[{"x":6811,"y":15551,"a":"a"},
{"x":6811,"y":15551,"a":"b"},
{"x":6811,"y":15551,"a":"c"},
{"x":6811,"y":15552,"a":"c"},
{"x":6812,"y":15551,"a":"c"}]
How to group by two property
The last result is
[{"x":6811,"y":15551,"a":["a","b","c"]},
{"x":6811,"y":15552,"a":["c"]},
{"x":6812,"y":15551,"a":["c"]}]
How to use underscore to make it unique and generate a merge "a" Key
回答1:
You can use groupBy
to create a composite key on x
and y
. Then, use map
to iterate through the grouped data.
var data = [{"x":6811,"y":15551,"a":"a"},{"x":6811,"y":15551,"a":"b"},{"x":6811,"y":15551,"a":"c"},{"x":6811,"y":15552,"a":"c"},{"x":6812,"y":15551,"a":"c"}]
var groups = _.groupBy(data, ({x,y}) => `${x}_${y}`);
var result = _.map(groups, o => ({...o[0], a : _.pluck(o,'a')}));
console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
回答2:
Here is a vanilla js solution using reduce
and Object.values
var output = Object.values( arr.reduce( (acc, c) => {
var {x,y} = c;
var key = JSON.stringify({x,y}); //create a key with both x and y
if ( acc[ key ] )
{
acc[ key ].a.push(c.a); //if key is already set, then push the value in a
}
else
{
acc[ key ] = c; //else set c as value for this key
acc[ key ].a = [acc[ key ].a];
}
return acc;
} ,{}) );
Demo
var arr = [{
"x": 6811,
"y": 15551,
"a": "a"
},
{
"x": 6811,
"y": 15551,
"a": "b"
},
{
"x": 6811,
"y": 15551,
"a": "c"
},
{
"x": 6811,
"y": 15552,
"a": "c"
},
{
"x": 6812,
"y": 15551,
"a": "c"
}
];
var output = Object.values(arr.reduce((acc, c) => {
var {
x,
y
} = c;
var key = JSON.stringify({
x,
y
}); //create a key with both x and y
if (acc[key]) {
acc[key].a.push(c.a); //if key is already set, then push the value in a
} else {
acc[key] = c; //else set c as value for this key
acc[key].a = [acc[key].a];
}
return acc;
}, {}));
console.log( output );
来源:https://stackoverflow.com/questions/49665676/underscore-nested-group-by-and-generate-a-json