Iterating a JavaScript object’s properties using jQuery
$.each( { name: “John”, lang: “JS” }, function(i, n){ alert( “Name: ” + i + “, Value: ” + n ); }); each
iteration
Is there a reason that we cannot iterate on “reverse Range” in ruby?
A range is just that: something defined by its start and end, not by its contents. “Iterating” over a range doesn’t really make sense in a general case. Consider, for example, how you would “iterate” over the range produced by two dates. Would you iterate by day? by month? by year? by week? It’s not … Read more
How do I access properties of a javascript object if I don’t know the names?
You can loop through keys like this: for (var key in data) { console.log(key); } This logs “Name” and “Value”. If you have a more complex object type (not just a plain hash-like object, as in the original question), you’ll want to only loop through keys that belong to the object itself, as opposed to … Read more
In Rust, is there a way to iterate through the values of an enum?
You can use the strum crate to easily iterate through the values of an enum. use strum::IntoEnumIterator; // 0.17.1 use strum_macros::EnumIter; // 0.17.1 #[derive(Debug, EnumIter)] enum Direction { NORTH, SOUTH, EAST, WEST, } fn main() { for direction in Direction::iter() { println!(“{:?}”, direction); } } Output: NORTH SOUTH EAST WEST
recursion versus iteration
Recursion is usually much slower because all function calls must be stored in a stack to allow the return back to the caller functions. In many cases, memory has to be allocated and copied to implement scope isolation. Some optimizations, like tail call optimization, make recursions faster but aren’t always possible, and aren’t implemented in … Read more
Remove Elements from a HashSet while Iterating [duplicate]
You can manually iterate over the elements of the set: Iterator<Integer> iterator = set.iterator(); while (iterator.hasNext()) { Integer element = iterator.next(); if (element % 2 == 0) { iterator.remove(); } } You will often see this pattern using a for loop rather than a while loop: for (Iterator<Integer> i = set.iterator(); i.hasNext();) { Integer element … Read more
Does pandas iterrows have performance issues?
Generally, iterrows should only be used in very, very specific cases. This is the general order of precedence for performance of various operations: vectorization using a custom Cython routine apply reductions that can be performed in Cython iteration in Python space itertuples iterrows updating an empty frame (e.g., using loc one-row-at-a-time) Using a custom Cython … Read more
C# Iterating through an enum? (Indexing a System.Array)
Array values = Enum.GetValues(typeof(myEnum)); foreach( MyEnum val in values ) { Console.WriteLine (String.Format(“{0}: {1}”, Enum.GetName(typeof(MyEnum), val), val)); } Or, you can cast the System.Array that is returned: string[] names = Enum.GetNames(typeof(MyEnum)); MyEnum[] values = (MyEnum[])Enum.GetValues(typeof(MyEnum)); for( int i = 0; i < names.Length; i++ ) { print(names[i], values[i]); } But, can you be sure that … Read more
Is there a way in Pandas to use previous row value in dataframe.apply when previous value is also calculated in the apply?
First, create the derived value: df.loc[0, ‘C’] = df.loc[0, ‘D’] Then iterate through the remaining rows and fill the calculated values: for i in range(1, len(df)): df.loc[i, ‘C’] = df.loc[i-1, ‘C’] * df.loc[i, ‘A’] + df.loc[i, ‘B’] Index_Date A B C D 0 2015-01-31 10 10 10 10 1 2015-02-01 2 3 23 22 2 … Read more
Javascript Set vs. Array performance
Ok, I have tested adding, iterating and removing elements from both an array and a set. I ran a “small” test, using 10 000 elements and a “big” test, using 100 000 elements. Here are the results. Adding elements to a collection It would seem that the .push array method is about 4 times faster … Read more