Concat String to Int in Javascript

Question

I've come across a rather annoying little Syntax Problem. I'm currently using Scissors a Node Module for handling pdf files.

The syntax for choosing some of the Pdfs pages is described in the Docs:

var scissors = require('scissors');
var pdf = scissors('in.pdf')
   .pages(4, 5, 6, 1, 12)

This actually works great for me, but I'd like to do this dynamically. How would I go about concatenating integers to commas in javascript? if I pass a string, the function doesn't work anymore.

Thanks a lot in advance

there's the ES6 spread syntax

Patrick Barr
– Patrick Barr

2017-07-28 15:06:05 +00:00
Commented Jul 28, 2017 at 15:06 — Patrick Barr
– Patrick Barr, Commented Jul 28, 2017 at 15:06

jmtalarn · Accepted Answer · 2017-07-28 15:06:56Z

2

You are passing n values as arguments to a function. If you concatenate it into a String you will pass only one argument, the concatenated String.

Probably you want to use the spread operator https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator

If you have the numbers into an array you want to pass them to the function like this:

var scissors = require('scissors');
var pages = [4, 5, 6, 1, 12];
var pdf = scissors('in.pdf')
   .pages(...pages);

answered Jul 28, 2017 at 15:06

jmtalarn

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Comments

Slava Eremenko · Accepted Answer · 2017-07-28 15:07:10Z

2

You can use Function.prototype.apply for this.

var scissors = require('scissors');
var pdf = scissors('in.pdf'),
    args = [4, 5, 6, 1, 12];

scissors.pages.apply(pdf, args);

answered Jul 28, 2017 at 15:07

Slava Eremenko

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lupz · Accepted Answer · 2017-07-28 15:21:29Z

You should be able to pass an array of page numbers to the function. I took a look at the scissors source code and they seem to actually take care of the arguments themselves:

/**
 * Creates a copy of the pages with the given numbers
 * @param {(...Number|Array)} Page number, either as an array or as     arguments
 * @return {Command} A chainable Command instance
 */
Command.prototype.pages = function () {
  var args = (Array.isArray(arguments[0])) ?
    arguments[0] : Array.prototype.slice.call(arguments);
  var cmd = this._copy();
  return cmd._push([
    'pdftk', cmd._input(),
    'cat'].concat(args.map(Number), [
      'output', '-'
      ]));
};

You can pass multiple arguments that will be combined to an array with Array.prototype.slice or just pass an array that will be used directly.

var scissors = require('scissors');

var pages = [];

/* collect desired pages */
pages.push(23);
pages.push(42);
pages.push(1337);

var pdf = scissors('in.pdf').pages(pages);

Greg Guida · Accepted Answer · 2017-07-28 15:08:56Z

0

I'm assuming you mean you want to pass an array of arguments to the pages function. You can achieve this with javascript's apply function

var scissors = require('scissors');
var pdf = scissors('in.pdf')

pdf.pages.apply(pdf, [4, 5, 6, 1, 12])

answered Jul 28, 2017 at 15:08

Greg Guida

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