ToCode Solution: תרגול מערכים ואובייקטים#2
ToCode Solution: תרגול מערכים ואובייקטים#2shlomitha wants to merge 1 commit intoynonp:masterfrom shlomitha:sol-html5-web-development.arrays-objects-lab
Conversation
| - * and prints their amount | ||
| - */ | ||
| function sum(){ | ||
| var arr= [].slice.call(arguments); |
There was a problem hiding this comment.
Since you're using reduce and arrow functions (which is awesome, but is only supported in newer browsers), you might as well use the nicer:
var arr = Array.from(arguments)
Or even better:
function sum(...args) {
// now args is a real array
return args.reduce((a,b) => a+b, 0);
}
There was a problem hiding this comment.
Also note the second argument to reduce is the initial value, which would save you the condition in the following line
| if (arr.length===0 ) | ||
| console.log(0); | ||
| else{ | ||
| console.log(arr.reduce((a,b)=>a+b)); |
There was a problem hiding this comment.
Returning the value is better than printing it
| function uniq(){ | ||
| var duplicatesArray= [].slice.call(arguments); | ||
| var uniqueArray = duplicatesArray.filter(function(elem, pos) { | ||
| return duplicatesArray.indexOf(elem) == pos; |
There was a problem hiding this comment.
Not a good idea.
The filter runs over all elements in the original array for each item, resulting in O(n^2) complexity.
JavaScript objects can be used as hash maps, which gives you much better performance and cleaner code. Remember that:
found = {};
found['foo'] = true
// now foo is in the map found
typeof found['foo'] !== 'undefined'
// and bar is not
typeof found['bar'] === 'undefined'
Please Fix:
- Don't duplicate the array upfront
- Use an object to remember which items were found
- Create the new array of unique values as you iterate the original one
This should result in O(n) complexity and nicer code.
(*) Bonus: Read on maps here:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map
| var uniqueArray = duplicatesArray.filter(function(elem, pos) { | ||
| return duplicatesArray.indexOf(elem) == pos; | ||
| }); | ||
| console.log(uniqueArray); |
There was a problem hiding this comment.
Better to return a value than to print it
2 participants
No description provided.