npm install ol-proj-ch

import olpjch from 'ol-proj-ch'

/* GCJ02 */
const GCJ02 = olpjch.GCJ02
const code = GCJ02.CODE
//...

/* BD09 */
const BD09 = olpjch.BD09
const code = BD09.CODE

//or import GCJ02, BD09 or others
import {GCJ02} from 'ol-proj-ch'
import {BD09} from 'ol-proj-ch'
const code1 = GCJ02.CODE    //the code of GCJ02
const code2 = BD09.CODE     //the code of BD09

import {GCJ02} from 'ol-proj-ch'
import {transform} from 'ol/proj'
const coords = [117.0,32.0];
const newCoords = transform(coords, GCJ02.CODE, "EPSG:4326");

import {GCJ02} from 'ol-proj-ch'
import {transform} from 'ol/proj'
const coords = [117.0,32.0];
const newCoords = transform(coords, GCJ02.CODE, "EPSG:3857");

import {GCJ02} from 'ol-proj-ch'
import {GeoJSON} from "ol/format";

//geojson data pretend coordinates are in GCJ02
const data = {
   "type": "Feature",
   "geometry": {
      "type": "Point",
      "coordinates": [125.6, 10.1]
   },
   "properties": {
      "name": "Dinagat Islands"
   }
};

const format = new GeoJSON();
let feature = format.readFeature(data, {
   dataProjection: GCJ02.CODE,
   featureProjection: "EPSG:3857"
});
//... then add feature to layer and then add to map

import {GCJ02} from 'ol-proj-ch'
import WKT from "ol/format/WKT";

//WKT data
const data = `POINT (125.6 10.1)`;

const format = new WKT();
let feature = format.readFeature(data, {
   dataProjection: GCJ02.CODE,
   featureProjection: "EPSG:3857"
});
//... then add feature to layer and then add to map