When using recursion, you must be mindful of the dreaded infinite loop. Using the recursive function that we’ve built up over the previous lessons, we look at how a simple duplicated configuration item could cause chaos for our program as it has no context of which items it has previously seen. We fix this problem by introducing a parents array, which can keep track of which top-level commands have already been accessed.
Previous:
let input, config;
input = ['dist'];
config = {
"dist": ["build", "deploy"],
"build": ['js', 'css', 'vender'],
"js": ['babel', 'ng-Annotate', "uglify"],
"css": ["sass", "css-min"]
};
var res = getTasks(config, input, []);
function getTasks(config, input, initial){
return input.reduce((prev, next)=>{
if(config[next]){
return getTasks(config ,config[next], prev);
}else{
return prev.concat(next);
}
}, initial);
};
console.log(res);
----------
Code:
let input, config;
input = ['dist'];
config = {
"dist": ["build", "deploy"],
"build": ['js', 'css', 'vender', 'dist'],
"js": ['babel', 'ng-Annotate', "uglify"],
"css": ["sass", "css-min"]
};
var res = getTasks(config, input);
function getTasks(config, input, initial, parent){
initial = initial || [];
parent = parent || [];
return input.reduce((prev, next)=>{
if(parent.indexOf(next) > -1){
console.log('infinite loop detected!');
return prev;
}
if(config[next]){
return getTasks(config ,config[next], prev, parent.concat(next));
}else{
return prev.concat(next);
}
}, initial);
};
console.log(res);