This is a simple W65C02S assembler, it doesn't support all OpCode, you are welcome to complement it.
The code to call it is available in src/main.tsx for your reference.
Go to https://w6502.aloen.to and open DevTools (usually F12) and switch to Console tab
then you'll see some sample output.
And you can also try to assemble your own ASM.
For example:
console.log(Assembler(`
start:
jmp start
mov a, 0x11
mov [0x3000], x
mov y, 0x21
inc x
addc a, 0x02
`));