how to call function in node loop one at a time - node.js

Question

this block of code process else block first and then if block, for all request at once, i need a code that execute 5 iterations stop for 15 sec. and then again continue from next 5 iterations and so on.
function passotken(token, callback) {
async.waterfall([
function(callback) {
db.executesql("select top 20 ext_id as EMPNUM , data as datae from newtable", function (data, err) {
callback(null, data);
});
},
function(data, callback) {
var _json_parse = JSON.parse(JSON.stringify(data));
var rows = data.length;
console.log(rows)
var cnt = 1;
for (var row = 1; row <= rows; row++) {
logger.info(_json_parse[row-1].EMPNUM);
//console.log(dateFormat(_json_parse[row].datae));
var req = 'https://pratik.com/ta/rest/v2/companies/|RHV/employees/|' +_json_parse[row-1].EMPNUM + '/timesheets?date=' + dateFormat(_json_parse[row-1].datae, "isoDate");
//console.log(req);
var myXMLText = req;
reques.push(myXMLText);
}
// console.log(reques);
for (var a = 0; a < rows; a++) {
//CURRENTLY PROCESSING ALL REQUEST IN IF BLOCK AND STOP FOR 15 SEC FOR ONLY FIRST IF CONDITION AFTER THAT ALL IF CONDITION PROCESSING WITHOUT HALT
if(a%5==0)
{
console.log("if");
//console.log(reques[a]);
//postreq(reques[a],token,sleeped(a));
/* setTimeout(function(){sleeped(reques[a],token);;
},15000); */
sleeped(reques[a],token);
//SHOULD PROCESS IF BLOCK ONCE AND STOP FOR 15 SEC
}
else
{
postreqELSE(reques[a],token);
//SHOULD PROCESS ALL REQUECT IN ELSE BLOCK TILL IF CONDITION ABOVE NOT SATISY
}
}
Promise.all(ps)
.then((results) => {
console.log("results"); // Result of all resolve as an array
}).catch(err => console.log("err"));
},
], function(err, result) {
if (!err)
console.log("Successfully completed")
else console.log(err);
});
};
function callback() {
console.log("completed successfully");
}
function postreq(request1,token)
{
//BLOCK
}
function sleeped(requesarr,token)
{
console.log("in sleeping");
//console.log(requesarr,token)
setTimeout(function(){
postreq(requesarr,token);
},15000);}
function postreqELSE(request2,token1)
{
console.log("in 3RD function");
//BLOCK2
}

Answer 1

Sure, this question was answered previously here: What is the JavaScript version of sleep()?
Following is an example which will do what you're requesting:
var reques = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20];
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
async function checkLoop()
{
for (var a = 0; a < 20; a++)
{ console.log("["+a+"] a%5 is: "+a%5);
console.log ( new Date().toLocaleTimeString());
if(a%5==0)
{ console.log("if");
console.log ( new Date().toLocaleTimeString());
await sleep(15000);
}
else
{ console.log("else");
console.log ( new Date().toLocaleTimeString());
}
}
}
checkLoop();
This prints out the following: (partial) Important to note that it will always pause on the first iteration because the index starts at 0, not 1.
[0] a%5 is: 0
8:58:38 AM
if
[1] a%5 is: 1
8:58:53 AM
else
8:58:53 AM
[2] a%5 is: 2
8:58:53 AM
else
8:58:53 AM
[3] a%5 is: 3
8:58:53 AM
else
8:58:53 AM
[4] a%5 is: 4
8:58:53 AM
else
8:58:53 AM
[5] a%5 is: 0
8:58:53 AM
if
8:58:53 AM
[6] a%5 is: 1
8:59:08 AM
else
8:59:08 AM
[7] a%5 is: 2
8:59:08 AM
else
8:59:08 AM
If you can't use async, then try this approach: (interval set at 1.5 secs for easier testing. just change the 1500 to 15000 to = 15 seconds)
var reques = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20];
var _interval;
var timeToWait = 1500;
function checkLoop(_init)
{
clearInterval(_interval);
console.log("checkLoop entered with value of: ", _init);
var start = (typeof(_init) == "undefined") ? 0 : _init;
console.log("start is: "+start);
for (var a = start; a < 20; a++)
{ console.log("["+a+"] a%5 is: "+a%5);
console.log ( new Date().toLocaleTimeString());
if(a%5==0)
{ console.log("if");
console.log ( new Date().toLocaleTimeString());
(function(_idx){_interval = setInterval(function(){checkLoop(_idx+1)}, timeToWait);})(a)
break;
}
else
{ console.log("else");
console.log ( new Date().toLocaleTimeString());
}
}
}
checkLoop();