using turf.points to assign each gis coordinate with related property?

i have a set of geo points, such as

let geo_points = [  
   { "lnglat":[100,50], "id": 1 },
   { "lnglat":[100,50], "id": 2 },
   ....
];

by using turf.js, I can transform the geo points with turf points in this method and try to see which points in the predefined geojson

let lnglats = _.map( geo_points, function(item){
    return item.lnglat;
});
let ids = _.map( geo_points, function(item){
    return item.id;
});
let points = turf.points( lnglats  );

let ptsWithin = turf.pointsWithinPolygon( points , predefined);

the output of turf.pointsWithinPolygon only shows the lnglat without id property.

Seeing the documentation, it can add property to points.

 turf.points( lnglats , ids );

trying the method above only add the same property to each point in lnglat array .

{ 
   type: 'FeatureCollection', features:
       [ {type: 'Feature', properties: [ 1, 2 ], geometry: {…}}
         {type: 'Feature', properties: [ 1, 2 ], geometry: {…}}
       ]
}

what I really need is

{ 
   type: 'FeatureCollection', features:
       [ {type: 'Feature', properties: 1, geometry: {…}}
         {type: 'Feature', properties: 2, geometry: {…}}
       ]
}

how would I assign each point with lnglat and related id

Turf has no knowledge of your ids so can't pass them back in the result. Instead, try creating a Feature for each point, which can have its own embedded properties.

const geo_points = [{
    "lnglat": [100.1, 50.1],
    "id": 1
  },
  {
    "lnglat": [100.2, 50.2],
    "id": 2
  },
];

const poly = turf.polygon([
  [
    [99, 49],
    [99, 51],
    [101, 51],
    [101, 49],
    [99, 49]
  ]
]);

const pts = geo_points.map(function(item) {
  // Create a Feature<Point> for each geo_point, embedding the id as a property. 
  return turf.point(item.lnglat, {
    id: item.id
  });
});

const ptsWithin = turf.pointsWithinPolygon(turf.featureCollection(pts), poly);

console.log(ptsWithin);

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