I would like to use the reduce function instead of doing this:
var result = '';
authors.forEach(
function(author) {
result += author.name + ', ';
}
);
console.log(result);
So in the array authors there are several names. Now I want to build a string with this names, separated by comma (except the last one).
var result = authors.reduce(function (author, index) {
return author + ' ';
}, '');
console.log(result);
A flurry of answers just came in and here is one more!
The first option is using the native js join method which eliminates the need for reduce. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/join
var authors = ['some author', 'another author', 'last author'];
var authorString = authors.join(",");
console.log(authorString);
IMPORTANT - if you're array contains objects, then you might want to map it before joining:
var authors = [{name: 'some author'},{name: 'another author'},{name: 'last author'}]
var authorString = authors.map(function(author){
return author.name;
}).join(",");
console.log(authorString);
or, if you're really fired up about using reduce, just make sure you use the previous value, current value and index when passing in the callback. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
var authorString = authors.reduce(function(prevVal,currVal,idx){
return idx == 0 ? currVal : prevVal + ', ' + currVal;
}, '')
console.log(authorString);
IMPORTANT - again if your array contains objects then you will want to make sure you are using the 'name property':
var authors = [{name: 'some author'},{name: 'another author'},{name: 'last author'}];
var authorString = authors.reduce(function(prevVal,currVal,idx){
return idx == 0 ? currVal.name : prevVal + ', ' + currVal.name;
}, '')
console.log(authorString);
var authors = [{ name: "a" }, { name: "b" }, { name: "c" }]; var res = authors.reduce((prev, curr) => (prev.name ? prev.name : prev) + ', ' + curr.name); console.log(res);
Right, so it's an object. Let's map the names first then:
var result = authors.map(function( author ) {
return author.name;
}).join(', ');
join the names. To get names, you use map. map is great at plucking properties from objects.var names = authors.map(function(author) { return author.name; }); var result = names.join(', ');You are reinventing join()
var authors = ["a","b","c"];
var str = authors.join(", ");
console.log(str);if you want to use reduce add an if check
var authors = ["a","b","c"];
var result = authors.reduce(function (author, val, index) {
var comma = author.length ? ", " : "";
return author + comma + val;
}, '');
console.log(result);Since I missed the mapping part to make people happy...
var authors = [{
name: "a"
}, {
name: "b"
}, {
name: "c"
}];
var res = authors.map( function(val) { return val.name; }).join(", ");
console.log(res);OR
var authors = [{
name: "a"
}, {
name: "b"
}, {
name: "c"
}];
var result = authors.reduce(function(author, val, index) {
var comma = author.length ? ", " : "";
return author + comma + val.name;
}, '');
console.log(result);
var authors = [{ name: "a" }, { name: "b" }, { name: "c" }]; var res = authors.reduce((prev, curr) => (prev.name ? prev.name : prev) + ', ' + curr.name); console.log(res);
authors.map(({ name }) => name).join(", "), alternatively: authors.map(({ name }) => name).reduce((a, b) => a === "" ? a : `${a}, ${b}`, "").I came across this also. Most of these answers dont take into account that you want the authors name, meaning you have an array of objects.
A one line solution:
authors.reduce((prev, curr) => [...prev, curr.name], []).join(', ');
map is better suited for this. authors.map(({ name }) => name).join(", ")Try this:
var authors = ["Mikel", "Brad", "Jessy", "Pof", "MArting"]
var result = authors.reduce( (prev, curr) => prev +', '+ curr )
console.log(result)I will add my 2 cents, two options here, either through map or using ternary operator:
const authors = [{name: 'John'}, {name: 'Jack'}, {name: 'Charles'}];
// Map
const reducedMap = authors.map(a => a.name).reduce((result, name) => `${result},${name}`);
// Ternary operator and initial value
const reducedTernary = authors.reduce((result, author) => `${result}${result ? ',' : ''}${author.name}` , '');
// Result :
// John,Jack,Charles
Here is a "Python Like" method to build a string in one line using an array or an Object.
// From an Array
['Hey', 'Hi', 'Hello!'].reduce((result, item, index) => (index !==0 ? `${result}, `: '')+`${item}`, '')
// From an Object
Object.entries({one: 1, two: 2, three: 3}).reduce((result, [key, value], index) => (index !==0 ? `${result}, `: '')+`${key} -> ${value}`, '')
I hope this helps. Cheers.
