RunKit + npm: to-json-schema

var toJsonSchema = require("to-json-schema") const data = {"temperature":"+24 °C","wind":"11 km/h","description":"Sunny","forecast":[{"day":"1","temperature":"21 °C","wind":"7 km/h"},{"day":"2","temperature":"7 °C","wind":"6 km/h"},{"day":"3","temperature":"10 °C","wind":" km/h"}]} const options = { postProcessFnc: (type, schema, obj, defaultFnc) => ({ ...defaultFnc(type, schema, obj), type: [type, 'null'], }), objects: { postProcessFnc: (schema, obj, defaultFnc) => ({ ...defaultFnc(schema, obj), required: Object.getOwnPropertyNames(obj), }), } } console.log(toJsonSchema(data, options))