使用Underscore / Lodash在javascript中进行非变异反尾的最佳方法

Question

I'm an avid user of lodash/underscore in my node.js projects, and I find myself in a situation where I need to recursively iterate through an array from right to left in a manner similar to the below code (assuming that all calls are synchronous):

function makeDir(pathArray) {
  var unsulliedPath = clone(pathArray);
  var lastGuy = pathArray.pop();
  var restOfEm = pathArray;
  if dirExists(unsulliedPath) {
    console.log("Your job is done!");
  } else {
    makeDir(restOfEm);
    makeDir(unsulliedPath);
  }
}

Having to clone and mutate the pathArray argument bugs me, however. So I could do this:

function makeDir(pathArray) {
  var lastGuy = _.last(pathArray);

  // EITHER I could...
  var restOfEm = _(pathArray).reverse().tail().reverse().value(); 
  // OR I could do...
  var restOfEm = _.first(pathArray, pathArray.length - 1);

  if dirExists(pathArray) {
    console.log("Your job is done!");
  } else {
    makeDir(restOfEm);
    makeDir(pathArray);
  }
}

Okay, that takes care of having to clone the argument passed in. That underscore incantation is slightly ugly, though.

Do lodash/underscore contain a simpler and clearer method for getting the inverse of _.rest(), that is, every element except the last? If not, is there a preferred idiomatic solution for implementing this method in Javascript for use alongside lodash/underscore-style functional libraries, or is this simply nit-picking?

Thanks in advance, and apologies for any glaring omissions or errors in my question.

Answer 1

Why bother with underscore/lodash.

var last = pathArray.slice(-1)[0];
var rest = pathArray.slice(0, -1);

slice will do this all for you very easily...

Answer 2

Use Array.splice https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice and if you do not want to modify the original, do Array.slice to copy the original and then Array.splice.

ie:

var rest = pathArray.slice(0);
var last = rest.splice(-1, 1)[0];