An unspent transaction output (UTXO) selection module for bitcoin.
WARNING: Value units are in satoshis, not Bitcoin.
| Module | Algorithm | Re-orders UTXOs? |
|---|---|---|
require('coinselect') | Blackjack, with Accumulative fallback | By Descending Value |
require('coinselect/accumulative') | Accumulative - accumulates inputs until the target value (+fees) is reached, skipping detrimental inputs | - |
require('coinselect/blackjack') | Blackjack - accumulates inputs until the target value (+fees) is matched, does not accumulate inputs that go over the target value (within a threshold) | - |
require('coinselect/break') | Break - breaks the input values into equal denominations of output (as provided) | - |
require('coinselect/split') | Split - splits the input values evenly between all outputs, any provided output with .value remains unchanged | - |
Note: Each algorithm will add a change output if the input - output - fee value difference is over a dust threshold.
This is calculated independently by utils.finalize, irrespective of the algorithm chosen, for the purposes of safety.
Pro-tip: if you want to send-all inputs to an output address, coinselect/split with a partial output (.address defined, no .value) can be used to send-all, while leaving an appropriate amount for the fee.
letcoinSelect=require('coinselect')letfeeRate=55// satoshis per byteletutxos=[
...,{txId: '...',vout: 0,
...,value: 10000}]lettargets=[
...,{address: '1EHNa6Q4Jz2uvNExL497mE43ikXhwF6kZm',value: 5000}]// ...let{ inputs, outputs, fee }=coinSelect(utxos,targets,feeRate)// the accumulated fee is always returned for analysisconsole.log(fee)// .inputs and .outputs will be undefined if no solution was foundif(!inputs||!outputs)returnlettxb=newbitcoin.TransactionBuilder()inputs.forEach(input=>txb.addInput(input.txId,input.vout))outputs.forEach(output=>{// watch out, outputs may have been added that you need to provide// an output address/script forif(!output.address){output.address=wallet.getChangeAddress()wallet.nextChangeAddress()}txb.addOutput(output.address,output.value)})