user88169: So, Let's say I want to create a transaction by using bitcoinjs-lib.
As far as I can see, this library doesn't provide the help so that it can automatically figure out/grab unpent transactions for inputs and create a transaction magically.
My question is: Am I the one who has to know unspent transactions that I want to use for the inputs in advance ?
If the answer is no, then can you point me to the bitcoinjs-lib file that does this ?
If the answer is yes, how do I get unspent transactions ? By looking at my transaction list on blockchain and getting each one of them's txid and vouts seem not reasonable. Any idea ?

user26873: Yes you need to provide the UTXO details when building a transaction in bitcoinjs. One should not have to trust a library to provide blockchain data, the library works like a calculator and processes the data that it is given. It's not unreasonable at all, these details are easy to get from your node or an explorer.

88169: <p>So, Let's say I want to create a transaction by using <code>bitcoinjs-lib</code>.</p>
<p>As far as I can see, this library doesn't provide the help so that it can automatically figure out/grab unpent transactions for inputs and create a transaction magically.</p>
<p>My question is: Am I the one who has to know unspent transactions that I want to use for the inputs in advance ?</p>
<p>If the answer is <code>no</code>, then can you point me to the <code>bitcoinjs-lib</code> file that does this ?</p>
<p>If the answer is <code>yes</code>, how do I get unspent transactions ? By looking at my transaction list on blockchain and getting each one of them's txid and vouts seem not reasonable. Any idea ?</p>
 26873: <p>Yes you need to provide the UTXO details when building a transaction in bitcoinjs. One should not have to trust a library to provide blockchain data, the library works like a calculator and processes the data that it is given. It's not unreasonable at all, these details are easy to get from your node or an explorer.</p>
