For example there are two array of object and you want to print out each element, it is bad if you use two forEach method on each array:
var people1 = [ { name: ‘Mikko‘ }, { name: ‘Radu‘ } ]; var people2 = [ { name: ‘Jarno‘ }, { name: ‘Jussi‘ } ]; people1.forEach( (person) => { console.log(person.name); }); people2.forEach( (person) => { console.log(person.name); });
If use concat() can solve the problem:
var people1 = [ { name: ‘Mikko‘ }, { name: ‘Radu‘ } ]; var people2 = [ { name: ‘Jarno‘ }, { name: ‘Jussi‘ } ]; people1 .concat(people2) .forEach( (person) => { console.log(person.name); });
原文：http://www.cnblogs.com/Answer1215/p/4862764.html