While JavaScript didn't have BigInt until a couple years ago, it did start with all numbers being floats. JSVMs optimize heavily for the small integer (SMI) cas

While JavaScript didn't have BigInt until a couple years ago, it did start with all numbers being floats. JSVMs optimize heavily for the small integer (SMI) case. They do both dynamic profiling, speculative optimization, and significant type analysis to get very good code for the SMI cases.