Given a command queue looking something like the following . .
var commandQueue = [
function() {thing(100, 0, shiftFunc)},
function() {thing(100, 233, shiftFunc)},
function() {thing(100, 422, shiftFunc)}
];
How can I write a function that takes the commandQueue as a parameter and returns the sum of the second arguments (index [1]) to the functions in the queue without calling the functions in the queue?
You could use Function#toString and a regular expression, which search for the value between the first and second comma.
var commandQueue = [
function() {thing(100, 0, shiftFunc)},
function() {thing(100, 233, shiftFunc)},
function() {thing(100, 422, shiftFunc)}
];
console.log(commandQueue.reduce(function (r, a) {
return r + +((a.toString().match(/,\s*(\d+),/) || [])[1] || 0);
}, 0));This isn't possible, unfortunately. JavaScript provides no ability to peek inside a function definition.
You could rewrite it a little and then use map:
function thing(a, b) {
return Math.pow(a * b, 2);
}
var commandQueue = [
function() {
return thing(100, 0);
},
function() {
return thing(100, 233) % 6;
},
function() {
return thing(100, 422) % 6;
}
];
var commandResults = commandQueue.map(function(a) {
return a();
});
console.log(commandResults);
var commandQueue = [
function() {thing(100, 0, shiftFunc)},
function() {thing(100, 233, shiftFunc)},
function() {thing(100, 422, shiftFunc)}
];
function getThingSecondArg(fn) {
return +/thing\([^,]*,([^,]*)/.exec(fn)[1].trim();
};
function sum(arr) {
for (var i=0, result=0; i<arr.length; i++) {
result += arr[i];
}
return result;
}
console.log(sum(commandQueue.map(getThingSecondArg)));You can do it like this:
const sum = commandQueue.reduce((acc, val) =>
Number(val.toString().split(',')[1]) + acc, 0);
console.log(sum);