I'm quite new to programming, and I feel that similar questions have been asked before. But I've tried to apply them and know I am missing something fundamental.
Given an array:
var myArray = [24.203, 12*45, 000-1, 4567+00];
I'd like to strip all non integers, so that I have something like this:
var myArray = [24203, 1245, 0001, 456700];
I know of the .replace method, but I can't seem to get it work. Here are four things I've tried:
function stripNonIntegers(arr) {
var x;
this.myArray = myArray;
for(x = 0; x < 10; x++) {
myArray[x] = myArray[x].replace(/\D/g, '');
} }
stripNonIntegers(myArray);
This returns an error saying myArray is undefined.
var x;(myArray); { //I don't like the semicolons but I get an error if I omit them
for(x = 0; x < 10; x++)
{myArray[x] = myArray[x].replace(/\D/g, '');
} }
this returns an error saying x is undefined.
stripNonIntegers= function(arr) {
for (x =0; x<this.length; x++)
myArray.replace(/\D/g,'');};
stripNonIntegers(myArray);
This output is undefined.
var stripNonIntegers= myArray[x]; {
for (x=0; x<myArray.length; x++) {
stripNonIntegers = myArray.replace(/[^\d]/g, '');
} }
And this one also says x is undefined. This post explains how to use the .replace method with a regex of /D to strip non-numerics from a string, but I can't seem to get it to work with an array (not a function). Thus I try to stick a 'for' loop in there so it treats each element as its own string. I know I'm making a stupid mistake, but for all my trying, I can't identify it. I'm shooting in the dark.
Any tips? Thanks in advance.
var myArray = ['24.203', '12*45', '000-1', '4567+00'];
var myNewArray = myArray.map(function(value) {
return parseInt(value.replace(/\D/g, ''), 10);
});
\D is a shorthand character class that matches all non-digits.
The above code works when your array elements are strings.
You have the regular expression right, and you're using replace correctly. Your problem may be that the items in your array are not strings in the code you gave. Just wrap each one in quotes to make them strings:
var myArray = ['24.203', '12*45', '000-1', '4567+00'];
Then, you can map over the array and use your replace call:
var newArray = myArray.map(function (item) {
return item.replace(/\D/g, '');
});
That results in this:
["24203", "1245", "0001", "456700"]
These are still strings, though. To convert them to numbers, you can use parseInt:
var intArray = newArray.map(function (item) {
return parseInt(item, 10);
});
You could do all this in one step, if you prefer:
var newIntArray = myArray.map(function (item) {
return parseInt(x.replace(/\D/g, ''), 10);
});
Of course, if you prefer regular for loops, you could do all this with those. However, I think using map looks a bit cleaner. If you're not familiar with map, check out the MDN docs for the array map function
Related
I have not been coding for long and ran into my first issue I just can not seem to figure out.
I have a string "XX|Y1234$ZT|QW4567" I need to remove both $ and | and push it into an array like this ['XX', 'Y1234', 'ZT', 'QW4567'].
I have tried using .replace and .split in every way I could like of
var array = "XX|Y1234$ZT|QW4567"
var array2 = [];
array = array.split("$");
for(i = o; i <array.length; i++)
var loopedArray = array[i].split("|")
loopedArray.push(array2);
}
I have tried several other things but would take me awhile to put them all down.
You can pass Regex into .split(). https://regexr.com/ is a great tool for messing with Regex.
// Below line returns this array ["XX", "Y1234", "ZT", "QW4567"]
// Splits by $ and |
"XX|Y1234$ZT|QW4567".split(/\$|\|/g);
Your code snippet is close, but you've messed up your variables in the push statement.
var array = "XX|Y1234$ZT|QW4567"
var array2 = [];
array = array.split("$");
for (i = 0; i < array.length; i++) {
var loopedArray = array[i].split("|")
array2.push(loopedArray);
}
array2 = array2.flat();
console.log(array2);
However, this can be rewritten much cleaner using flatMap. Also note the use of let instead of var and single quotes ' instead of double quotes ".
let array = 'XX|Y1234$ZT|QW4567'
let array2 = array
.split('$')
.flatMap(arrayI => arrayI.split('|'));
console.log(array2);
And lastly, split already supports multiple delimiters when using regex:
let array = 'XX|Y1234$ZT|QW4567'
let array2 = array.split(/[$|]/);
console.log(array2);
You can do this as follows:
"XX|Y1234$ZT|QW4567".replace('$','|').split('|')
It will produce the output of:
["XX", "Y1234", "ZT", "QW4567"]
If you call the split with two parameters | and the $ you will get an strong array which is splittend by the given characters.
var array = "XX|Y1234$ZT|QW4567";
var splittedStrings = array.Split('|','$');
foreach(var singelString in splittedStrings){
Console.WriteLine(singleString);
}
the output is:
XX
Y1234
ZT
QW4567
I'm confused as to why my code is pushing every permutation twice. Please someone help. I'm using heap's algorithm:
var regex = /(.)\1+/g;
function permAlone(str) {
var newArray = str.split('');
var n = newArray.length;
var permutations = [];
var tmp;
function swap(index1, index2) {
tmp = newArray[index1];
newArray[index1] = newArray[index2];
newArray[index2] = tmp;
}
function generate(n, newArray) {
if (n === 1) {
permutations.push(newArray.join(''));
} else {
for(var i = 0; i<n-1; i++) {
generate(n-1, newArray);
swap(n % 2 ? 0 : i, n-1);
permutations.push(newArray.join(''));
}
generate(n-1, newArray);
}
}
generate(n, newArray);
return permutations;
}
permAlone('aab');
The array that is returned is:
["aab", "aab", "aab", "baa", "baa", "aba", "aba", "aba", "baa", "baa"]
So as you can see, the permutations are appearing many more times than intended for each thing. Any help would be great
The code's a little complex and it's difficult to track given the recursion, but if all you want is an array with only unique values, you can simply apply the following code to the result array:
function stripDuplicates(input) {
if (!input || typeof(input) !== 'object' || !('length' in input)) {
throw new Error('input argument is not array.');
}
var newArray = [];
for (var i = 0; i < input.length; i++) {
if (newArray.indexOf(input[i]) === -1) {
newArray.push(input[i]);
}
}
return newArray;
}
This could also be done functionally rather than imperatively, but that's really more of a preference than an optimization issue.
Bálint also points out that you could merely convert the result to a Set, then convert the Set back to an Array, which would automatically strip out any duplicates. Beware, though, that Set is a comparatively new affordance in Javascript and will not function in pre-ES6 environments.
You have a call to:
permutations.push(newArray.join(''));
inside of your for loop. That shouldn't be there. And then, of course if you are permuting strings that have duplicate characters, well, expect to see dupes. e.g., if you permute the string "aa" you'll get two entries from this algorithm "aa" and "aa". Heap's algorithm doesn't try to remove dupes, it treats each element as unique within the string. Obviously, it's trivial to use remove dupes if that's something you care about doing.
I'm trying to get the function below to return the average of all elements in array1, but I keep getting null as the result. I can't seem to figure out why.
var array1 = [46,73,-18,0,-442,779,5,1400];
var arrayAverage = function(arrayavg) {
for (var average = 0,answer=0, arrayavg = arrayavg.length;array1 > answer;answer++)
average +=parseInt(arrayavg[answer]);
var calc = average/arrayavg.length;
return calc
};
There are a number of errors, I don't have time to point them all out, hopefully the following is sufficient:
var array1 = [46,73,-18,0,-442,779,5,1400];
var arrayAverage = function(arrayavg) {
I don't know why you using a function expression rather than a function declaration. It doesn't affect the issue, but is more code to write. It's also good to give variables names that express what they are for, so given that the function expects an array:
function arrayAverage(array) {
then:
for (var average = 0,answer=0, arrayavg = arrayavg.length;array1 > answer;answer++)
It's not a good idea to pile all those variable declarations into the for condition, far better to separate concerns and only create variables that you need:
var total = 0;
Now iterate over the array to get the total value. The '{' brackets can be omitted, but it's clearer to include them:
for (var i=0, iLen=array.length; i<iLen; i++) {
total += array[i];
}
Now calculate the average and return it in one statement:
return total/iLen;
}
console.log(arrayAverage(array1)); // 230.375
You need to put brackets after your for loop
I was too fast to answer.
You are re-assigning the passed array to the length of the passed array.
arrayavg = arrayavg.length
this breaks everything.
in the for loop you have assigned arrayavg=arrayavg.length and in the body ,you are accessing average+=arrayavg[answer]. arrayavg is now a primitive type . it will return undefined.
And your loop condition is array1 > answer array1 is an array .you cant compare it like that.it will return false.
modified code.
var array1 = [46,73,-18,0,-442,779,5,1400];
var arrayAverage = function(arrayavg) {
var sum=0;
for (var i=0;i<arrayavg.length;i++)
sum +=parseInt(arrayavg[i]);
return sum/arrayavg.length;
};
You are comparing a number to your array in your for loop. You want to stop the for when answer is the same as array1 length.
Also, don't change your parameter array to its length if you want to get its values in the loop.
var array1 = [46,73,-18,0,-442,779,5,1400];
var arrayAverage = function(arrayavg) {
for (var average = 0,answer=0, len = arrayavg.length;len > answer;answer++)
average +=parseInt(arrayavg[answer]);
var calc = average/len;
return calc
};
And to call it:
arrayAverage(array1);
Your code has two problems in the for loop.
for (var average = 0,answer=0, arrayavg = arrayavg.length;array1 > answer;answer++)
^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^
First thing is you set arrayavg to arrayavg's length BUT in the next line you try to read the index of the array. Well you overwrote the array with a number! Not going to happen.
Second issue you are comparing an array 'array1' to a number 'answer' . What does that check do? Not what you think it is going. You want to be checking the length, but wouldn't you want to be checking the passed in array, not the hardcoded one?
I think the other answers (particularly RobG) have covered most of it. It might help to follow a couple of standard rules (that I use) for your loops:
1) Always have the index as the first declared element, the length of the array (for caching purposes) as the second, and any other variables after them.
2) Always use brackets to separate your loop code from the code in the rest of the function. That way you know when to return your averaged product (ie after the }).
So this is my slightly rewritten code of your problem:
for (var index = 0, len = arrayavg.length, avg = 0; index < len; index++) {
avg += parseInt(arrayavg[index], 10) / len;
}
return avg;
Note also that parseInt should contain a radix (in this case 10). You can leave it out but it's good practice to always include it.
By the way, here's an alternative to your function you might find useful that uses a functional approach using reduce:
var arrayAverage = function (arr) {
return arr.reduce(function (a, b) { return a + b; }) / arr.length;
}
I have some data that I'm trying to clean up. For the field in question, I know what the possible values are, but the value is stored in a concatenated string and I need them in an array. Here is what I would like to do:
var valid_values = ['Foo', 'Bar', 'Baz'];
var raw_data = ['BarFoo','BazBar','FooBaz'];
desired_result = [['Bar','Foo'],['Baz','Bar'],['Foo','Baz']];
I'm not sure what this is called, so I hope this isn't a duplicate.
You can iterate over each data value, searching for allowed string with indexOf or contains and returning successful matches as array.
Here's my version of code and working example at jsFiddle:
var out = raw_data.map(function (raw) {
return valid_values.filter(function (value) {
return raw.contains(value);
});
});
//out === [['Bar','Foo'],['Baz','Bar'],['Foo','Baz']];
I assumed that output match order isn't important.
This is assuming some things about your data:
you need to split strings into 2-item pairs
input & terms are case-sensitive
you won't be dealing with null/non-conforming inputs (requires more edge-cases)
In that case, you'd want to do something like this:
// for each item in the desired result, see if it's a match
// at the beginning of the string,
// then split on the string version of the valid value
function transform(input){
for(i = 0; i < len; i++) {
if (input.indexOf(valid_values[i]) === 0) {
return [ valid_values[i], input.split(valid_values[i])[1] ];
}
}
return [];
}
// to run on your input
var j = 0, raw_len = raw_data.length, desired_result = [];
for(; j < raw_len; j++) {
desired_result.push(transform(raw_data[j]));
}
This code is pretty specific to the answer you asked though; It doesn't cover many edge cases.
I have an ajax request that returns a list of values like this:
"1,2,3,4,5,6"
I need it to be a javascript array with numbers:
[1,2,3,4,5,6]
I tried:
var array = new Array("1,2,3,4,5,6".split(","))
But the numbers are still strings in the output:
["1","2","3","4","5","6"]
Is there a clean way to have it as a numbered array? Preferably without writing a function to iterate through it?
You need to loop through and convert them to numbers, like this:
var array = "1,2,3,4,5,6".split(",");
for(var i=0; i<array.length; i++) array[i] = +array[i];
Or, the more traditional example:
var array = "1,2,3,4,5,6".split(",");
for(var i=0; i<array.length; i++) array[i] = parseInt(array[i], 10);
A more jQuery-centric approach using jQuery.map():
var str = "1,2,3,4,5,6";
var arr = $.map(str.split(","), function(el) { return parseInt(el, 10); });
Not sure if this counts as writing a function but you can use the map function in jquery. I saw you listed as a tag so I assume you are using:
var stringArray = "1,2,3,4,5,6".split(",");
var numberArray = $.map(stringArray,
function(item, i)
{
return parseInt(item, 10);
});
// jquery must have a way to do what any modern browser can do:
var str= "1,2,3,4,5,6";
var arr= str.split(',').map(Number);
// returns an array of numbers
If you trust the ajax response, and if (for whatever reason) you're committed to not using a loop, you can always go with eval:
var str = "1,2,3,4,5,6";
var array = eval("[" + str + "]");
If you don't wish to expliclty iterate you can use array.map, javascripts map function.
array.map(callbackFunc, array);
var arr = array.map(function(x) {return parseInt(x);}, "1,2,3,4,5,6".split(","));
http://www.tutorialspoint.com/javascript/array_map.htm
Theres probably a better reference somewhere but I don't us javascript enough to have a good favorite reference site.
EDIT - i see jQuery has its own map, thats probably worth looking into.