pchain
pchain ensures execution sequence of multiple Promises, return a promise which rejects on the first rejection, or resolves when the last Promise is resolved.
Also, resolved data from a step is passed to the next step function as input parameter.
Example
Chain promises, or functions which return promise. Resolved data from a Promise will be passed to next step as function parameter, if the next step is a function:
var pchain = require('pchain');
pchain([
step1,
step2,
step3,
step4
]).then((data) => {
console.log('All set:', data);
}).catch((err) => {
console.log('Demo something wrong:', err);
});
function step1() {
return new Promise((resolve, reject) => {
console.log('step1');
resolve('result from step 1');
});
}
function step2(data) {
return new Promise((resolve, reject) => {
console.log('step2. Data:', data);
resolve();
});
}
function step3() {
return new Promise((resolve, reject) => {
console.log('step3: Random resolve or reject');
if (Date.now() % 2)
resolve();
else
reject('unlucky');
});
}
function step4() {
return new Promise((resolve, reject) => {
console.log('step4');
resolve("I'm lucky");
});
}
If any value is not a function but an object, it will be pased to the next step as parameter as well:
pchain([
'Parameter for the next step',
step1,
step2
]).then((data) => {
...
}).catch((err) => {
...
});
Enable verbose debug:
pchain.debug();
or
pchain = require('pchain').debug();
A chain name can be specified to the chain, for easier debug purpose:
var pchain = require('pchain').debug();
pchain([
step1,
step2,
pchain.sleep(2000), //utility to sleep
'Hello, mortal', //non-promise will be passed as parameter to next step
step3,
new Promise(resolve => { //bare promise can be used as well.
resolve();
}),
step5,
step6
], 'Demo sequence').then((data) => {
console.log('All set:', data);
}).catch((err) => {
console.log('Demo something wrong:', err);
});
function step1() {
return new Promise(resolve => {
resolve('result from step 1');
});
}
function step2(data) {
return new Promise((resolve, reject) => {
console.log('step2 - get data from previous step: ' + data);
resolve();
});
}
function step3(data) {
return new Promise((resolve, reject) => {
console.log('step3 - get data const: ' + data);
resolve();
});
}
function step5() {
return new Promise((resolve, reject) => {
console.log('step5 - Random resolve or reject');
if (Date.now() % 2)
resolve();
else
reject('unlucky');
});
}
function step6() {
return new Promise((resolve, reject) => {
resolve("I'm lucky");
});
}