Контантенировать два массива?

let teamsArray = ['a', 'b', 'c', 'd', 'e'] 
let teamsArrayNew = [1, 2, 3, 4, 5, 6, 7] 
 
function updateArray(entryArray, newArray) { 
  newArray = newArray.reverse(); 
  newArray.forEach(function(element) { 
    entryArray.unshift(element); 
    if (newArray.length <= 10) { 
      entryArray = entryArray.slice(0, 10); 
    } else { 
      entryArray = entryArray.slice(0, newArray.length); 
    } 
  }); 
  return entryArray; 
} 
 
teamsArray = updateArray(teamsArray, teamsArrayNew); 
 
console.log(teamsArray);