const poly = turf.polygon(obj.features[0].geometry.coordinates)
const point = turf.point(newPoint)const isWithinBoundary = turf.booleanPointInPolygon(point, poly)
console.log(isWithinBoundary, '点是否在面内')

ps：需要注意的是，
如果使用turf.polygon([[obj.features[0].geometry.coordinates]])，
那么他解析出来其实是turf.polygon([[[[[15445,15654],[15445,15654],[15445,15654],[15445,15654]]]]])，
所以不能额外添加[[]]，直接turf.polygon(obj.features[0].geometry.coordinates)即可