Reputation: 1674
I'm trying to get an array from each individual integer from the string. In Python, I would do:
string = '1234-5'
forbidden = '-'
print([int(i) for i in str(string) if i not in forbidden])
Does JavaScript have something similar?
Upvotes: 138
Views: 154917
Reputation: 2088
A bit late for the party, but as of 2024 I would do:
console.log(parseInt(string.split('').filter(i => !forbidden.includes(i))))
Upvotes: 1
Reputation: 10845
JavaScript doesn't need list comprehensions because map
and filter
work better in the language compared to Python.
In Python:
[int(i) for i in '1234-5' if i != '-']
# is equivalent to the ugly
list(map(lambda _: int(_),filter(lambda _: _!='-','1234-5')))
Whereas in JavaScript, map
and filter
are Array
methods, so:
[...'1234-5'].filter(_=> _!='-').map(_=> parseInt(_))
Upvotes: 3
Reputation: 12140
Given the question's Python code
print([int(i) for i in str(string) if i not in forbidden])
this is the most direct translation to JavaScript (ES2015):
const string = '1234-5';
const forbidden = '-';
console.log([...string].filter(c => !forbidden.includes(c)).map(c => parseInt(c)));
// result: [ 1, 2, 3, 4, 5 ]
Here is a comparison of the Python and JavaScript code elements being used: (Python -> Javascript):
Array.filter
Array.map
Upvotes: 28
Reputation: 267
You could have a look at CoffeeScript. CoffeeScript adds missing features to java-script and allows you to write cleaner, more readable code. https://coffeescript.org/#coffeescript-2
You write a .coffee file and the coffeScript-compiler compiles your coffee file into a JavaScript file. Because the translation into JavaScript happens by compiling, the script should not run any slower.
So your code would look like the following in coffee script:
string = '1234-5'
forbidden = '-'
alert(JSON.stringify(+i for i in string when i isnt forbidden))
Honestly, this is even easier to read then the python counterpart. And it compiles quickly to the fallowing JavaScript:
var forbidden, i, string;
string = '1234-5';
forbidden = '-';
alert(JSON.stringify((function() {
var j, len, results;
results = [];
for (j = 0, len = string.length; j < len; j++) {
i = string[j];
if (i !== forbidden) {
results.push(+i);
}
}
return results;
})()));
You don’t even need to install anything. On their website you can play around with it, and it will show you the translated JavaScript code.
Upvotes: 1
Reputation: 5813
Update: Array comprehensions were removed from the standard. Quoting MDN:
The array comprehensions syntax is non-standard and removed starting with Firefox 58. For future-facing usages, consider using Array.prototype.map, Array.prototype.filter, arrow functions, and spread syntax.
See this answer for an example with Array.prototype.map
:
let emails = people.map(({ email }) => email);
Original answer:
Yes, JavaScript will support array comprehensions in the upcoming EcmaScript version 7.
Here's an example.
var str = "1234-5";
var ignore = "-";
console.log([for (i of str) if (!ignore.includes(i)) i]);
Upvotes: 98
Reputation: 788
JavaScript no longer supports array comprehensions.
I too was looking for the JavaScript equivalent. Mozilla Developer's Network indicates that this functionality is no longer supported. The preferred syntax is referenced in the aforementioned link.
Upvotes: 4
Reputation: 49
You could easily achieve this behavior using an application functor.
Array.prototype.ap = function(xs) {
return this.reduce((acc, f) => acc.concat(xs.map(f)), [])
}
const result = [x => x +1].ap([2])
console.log(result)
Upvotes: 4
Reputation: 11
It does have a poor mans version
const string = '1234-5'
const forbidden = '-'
print([int(i) for i in str(string) if i not in forbidden])
const result = string.split('').filter(char => char !== forbidden);
console.log(result)
In JS you can only iterate over single elements in array, so no extraction of multiple entries at a time like in Python.
For this particular case you should use a RegExp to filter the string though.
Upvotes: 0
Reputation: 5813
For "completeness"-sake, here's a shorter regexp version.
var str = "1234-5";
var ignore = "-=";
console.log(str.replace(new RegExp(ignore.split("").join("|")), "").split(""));
EDIT: To make sure that RegExp does not "choke" on special characters, ignore
can be implemented as regexp literal, instead of a string:
var str = "1234-5";
var ignore = /[\+=-]/;
console.log(str.replace(ignore, "").split(""));
Upvotes: 2
Reputation: 1758
Not directly, but it's not hard to replicate.
var string = "1234-5";
var forbidden = "-";
string.split("").filter(function(str){
if(forbidden.indexOf(str) < 0) {
return str;
}
}).forEach(function(letter) { console.log(letter);});
I guess more directly:
for(var i=0 ; i < str.length ; i++) {
if(forbidden.indexOf(str) < 0) {
console.log(str[i]);
}
}
But there's no built in way to filter in your for loop.
Upvotes: 5
Reputation: 1
Reading the code, I assume forbidden can have more than 1 character. I'm also assuming the output should be "12345"
var string = "12=34-5";
var forbidden = "=-";
console.log(string.split("").filter(function(str){
return forbidden.indexOf(str) < 0;
}).join(""))
If the output is "1" "2" "3" "4" "5" on separate lines
var string = "12=34-5";
var forbidden = "=-";
string.split("").forEach(function(str){
if (forbidden.indexOf(str) < 0) {
console.log(str);
}
});
Upvotes: 10