node_modules/jszip/node_modules/core-js/modules/_ctx.js

// optional / simple context binding
var aFunction = require('./_a-function');
module.exports = function(fn, that, length){
  aFunction(fn);
  if(that === undefined)return fn;
  switch(length){
    case 1: return function(a){
      return fn.call(that, a);
    };
    case 2: return function(a, b){
      return fn.call(that, a, b);
    };
    case 3: return function(a, b, c){
      return fn.call(that, a, b, c);
    };
  }
  return function(/* ...args */){
    return fn.apply(that, arguments);
  };
};