Run results for: object.assign vs spread (when base object is large)

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 11_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15F79 MicroMessenger/6.7.0 NetType/WIFI Language/en

Browser: Mobile Safari 11

Operating system: iOS 11.4

Device Platform: Mobile

Date tested: 5 years ago

Test name	Executions per second
object.assign	1231920.0 Ops/sec
spread	46591.5 Ops/sec
without immutable	481139.4 Ops/sec

Script Preparation code:

var baseObj = {"field0":"value0","field1":"value1","field2":"value2","field3":"value3","field4":"value4","field5":"value5","field6":"value6","field7":"value7","field8":"value8","field9":"value9","field10":"value10","field11":"value11","field12":"value12","field13":"value13","field14":"value14","field15":"value15","field16":"value16","field17":"value17","field18":"value18","field19":"value19","field20":"value20","field21":"value21","field22":"value22","field23":"value23","field24":"value24","field25":"value25","field26":"value26","field27":"value27","field28":"value28","field29":"value29","field30":"value30","field31":"value31","field32":"value32","field33":"value33","field34":"value34","field35":"value35","field36":"value36","field37":"value37","field38":"value38","field39":"value39","field40":"value40","field41":"value41","field42":"value42","field43":"value43","field44":"value44","field45":"value45","field46":"value46","field47":"value47","field48":"value48","field49":"value49","field50":"value50","field51":"value51","field52":"value52","field53":"value53","field54":"value54","field55":"value55","field56":"value56","field57":"value57","field58":"value58","field59":"value59","field60":"value60","field61":"value61","field62":"value62","field63":"value63","field64":"value64","field65":"value65","field66":"value66","field67":"value67","field68":"value68","field69":"value69","field70":"value70","field71":"value71","field72":"value72","field73":"value73","field74":"value74","field75":"value75","field76":"value76","field77":"value77","field78":"value78","field79":"value79","field80":"value80","field81":"value81","field82":"value82","field83":"value83","field84":"value84","field85":"value85","field86":"value86","field87":"value87","field88":"value88","field89":"value89","field90":"value90","field91":"value91","field92":"value92","field93":"value93","field94":"value94","field95":"value95","field96":"value96","field97":"value97","field98":"value98","field99":"value99"}
var newObj = {"n0":"v0","n1":"v0","n2":"v0","n3":"v0","n4":"v0"}

Tests:

object.assign
var c = Object.assign(baseObj, newObj);
spread
var c = {...baseObj, newObj}
without immutable
Object.keys(newObj).forEach(key=>(baseObj[key]=newObj[key]))

Run results for: object.assign vs spread (when base object is large)

object.assign

spread

without immutable