Run promises sequentially in node.js - mysql

Question

I'm still figuring node.js and promises out.
There's an area in my code where I would like my sql statements to run sequentially.
I would like one sql statement to run once one sql statement is done. I'm not sure if I am implementing promises properly.
one of the sql statements:
var selectbotagentstoadd=new Promise((resolve,reject)=>{
var sql='SELECT tbltestbotagentstoadd.AgentID FROM tbltestbotagentstoadd WHERE tbltestbotagentstoadd.IDNumber=? AND tbltestbotagentstoadd.MSISDN=?;'
DB.query(sql,[agentidpassnum,agentnumber],function(err,results){
if (err){
return reject(err);
};
return resolve(results);
});
})
the promise statement:
await insertbotagentstoadd.then(()=>{
console.log("done with one");
})
.then(()=>{ selectbotagentstoadd.then((results)=>
{
AgenttoaddIDStore=[];
results.forEach(agent=>{
AgenttoaddIDStore.push({
AgentID:agent.AgentID
});
ctx.session.tempAgentID=agent.AgentID
});
console.log("agent ID: "+ctx.session.tempAgentID);
console.log("done with two");
})})
.then((results)=>{insertcctblricaagents
console.log("done with three");
})
.then((results)=>{selectcctblricaagents.then((result)=>{
console.log(result);
AgentnewIDStore=[];
result.forEach(agent=>{
AgentnewIDStore.push({
AgentID:agent.AgentID
})
ctx.session.AgentID=agent.AgentID
})
console.log("cctblricaagents agent ID: "+ ctx.session.AgentID);
console.log("done with four");
})})
.then(insertcctblricaagentsnum.then((result)=>{
console.log("done with five");
}))
.then(selectcctblricaagentsnum.then((result)=>{
console.log(result)
AgentIDStore=[];
result.forEach(agent=>{
AgentIDStore.push({
AgentID:agent.AgentID,
MainNumber:agent.MainNumber,
})
ctx.session.AgentID=agent.AgentID
ctx.session.agentnumber=agent.MainNumber
})
console.log("cctblricaagentsnum agent ID: "+ ctx.session.AgentID);
console.log("done with six");
}))
.then(insertcctblintblbotagents.then((result)=>{
console.log("done with seven");
}));
The results I get from the terminal:
Agent number: 27815567777
done with one
done with three
agent ID: 89
done with two
[]
cctblricaagents agent ID: null
done with four

Answer 1

If you properly return the promises in each of the then blocks, it should execute sequentially.
simplifying your code, for ex:
await insertbotagentstoadd
.then(() => {
console.log("done with one");
})
.then(() => selectbotagentstoadd)
.then((res) => {
console.log("done with two");
return res;
})
.then((results) => insertcctblricaagents)
.then((res) => {
console.log("done with three");
return res;
})
.then((results) => selectcctblricaagents)
.then((res) => {
console.log("done with four");
return res;
})
.then(() => insertcctblricaagentsnum)
.then((res) => {
console.log("done with five");
return res;
})
.then(() => selectcctblricaagentsnum)
.then((res) => {
console.log("done with six");
return res;
})
.then(() => insertcctblintblbotagents)
.then((res) => {
console.log("done with seven");
return res;
});
Edit:
How it will look with your calculation included:
await insertbotagentstoadd
.then(() => {
console.log("done with one");
})
.then(() => selectbotagentstoadd)
.then((results) => {
AgenttoaddIDStore = [];
results.forEach((agent) => {
AgenttoaddIDStore.push({
AgentID: agent.AgentID,
});
ctx.session.tempAgentID = agent.AgentID;
});
return AgenttoaddIDStore;
})
.then((res) => {
console.log("done with two");
return res;
})
.then((results) => insertcctblricaagents)
.then((res) => {
console.log("done with three");
return res;
})
.then((results) => selectcctblricaagents)
.then((result) => {
AgentnewIDStore = [];
result.forEach((agent) => {
AgentnewIDStore.push({
AgentID: agent.AgentID,
});
ctx.session.AgentID = agent.AgentID;
});
return AgentnewIDStore;
})
.then((res) => {
console.log("done with four");
return res;
});