In dynamically typed language, truthiness is a term used to describe a value that might evaluate to boolean true.
Questions tagged [truthiness]
99 questions
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how to check xpath expression (if valid/not) before scraping data with spider
Probably you have realized by title, I am using scrapy and xpath to extract data. I tried and provided xpaths from file to the spider (to make spider generic - not to edit often) As required, I am able to extract data in the format…
techDiscussion
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1
vote
1 answer
Object has value but does not appear to exist?
I have the following Python code:
if bedrooms: # bedrooms exists
.....
else: # BEDROOMS DOES NOT EXIST
bn = "BEDROOMS DOES NOT EXIST"
I was stepping through it in my debugger and noticed that even though bedroom == 0 , the flow jumps to…
user1592380
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In environments that take Boolean arguments, is it a good idea to wrap all functions instead of allowing them to be implicitly coerced?
Take the String#=~ function for instance. It will return the index of the first match if the match is found, which, as a Fixnum will always act as true in boolean environments. If the match isn't found, it returns null, which acts as false.
Now…
Steven
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How can I create a Proc to checking whether the elements of an array are nil or not?
I'm trying to solve this assignment:
Create a Proc that will check whether a given array of elements are nil or not. Use .nil? to evaluate elements. Print 'true' if the elements are nil and 'false' if the element has a [truthy] value.
This is my…
Dev
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.every() prototype isn't working as expected
Obviously it works for people so I must just be dumb, but I am passing an array of boolean's through the .every() prototype and it ALWAYS appears to return true, even when it shouldnt. so heres the code
The function call is made
checkAnswer();
Then…
Quinten Steenwyk
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0
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2 answers
Typescript optional function truthy check
I think I'm missing something basic on how you can check for a truthy value with && in Typescript.
Why can props.function still be undefined in test1 and has to be checked like I did in test2.
import React from "react";
interface PropsModel {
…
Sean A.S. Mengis
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Checking lots of variables for truthiness in a single pass
I have a large form with many fields and a special processing function
Several variables of different types declared at the beginning of a function
I would like to check that a user has set all variables before a function execution
const a1 = true,…
Igniter
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When I am testing for truthiness, why is my Object.create(null) value true while null is false?
I am trying to confirm for myself whether a null object is false.
First, I tried to create a null object using Object.create(null).
Then I decided to test this object against null.
I wrote a snippet of code to check for truthiness:
let emptyObject =…
0
votes
2 answers
Is !obj[key] a good practice to check the existence of an object's property in JavaScript?
Every now and then, I see this pattern:
if (!obj[key]) {
// key does not exist inside object
obj[key] = ...
} else {
// maybe do something else with obj[key]
}
but I find it extremely wrong. What if actually obj[key] has the value false…
but-why
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Is //(typeof(myVar) != "undefined")// logically equivalent to the truthy //if (myVar)?
Over a large project I do a lot of exception handling by explicitly checking whether a variable has been set using typeof. It's a bit verbose and I'd like to change my habit to a simple truthy:
if (myVar) {//do stuff}
In the snippet below and in…
Mark Taylor
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4 answers
comparing with `{}` and truthyness
I have an API that calls me with {} for a param that I need to replace.
But having trouble as in ... can you guess what happens below?
const log = console.log
const a = {}
log('a is ', a)
// cannot compare with either == or ===
if (a == {}) {
…
dcsan
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2 answers
How to run the logTruthiness function
This code given below is supposed to evaluate if a value coerces to true or false. How does this work? for example if I want to know if a string- "my string" will be coereced to true or false, how do I use the to determine that?
I have tried to…
sonali saha
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Python if statements and truth value testing for non compsci background
This aims to be a self answered question after a few hours of digging, I found this thought process may prove useful to others who also may not have come from a formal compsci background.
This all started from confusion over why one particular if…
topher217
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2 answers
Bash: Safe to remove all occurrences of -n inside brackets?
I recently found this "bug" in my bash script;
if [ "$var" ]; then
echo "Condition is true"
fi
where what I meant was to check if $var is non-empty, i.e. [ -n "$var" ]. As it happens, the code seems to work perfectly fine without the -n.…
jmd_dk
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2 answers
Anyone know why I'm getting a "Process finished with exit code 0"?
I'm trying to run this program but for some reason, whenever I enter 0, the program stops running. I expect a "You've guessed too low, please try again " as the input is less than the random number generated. Can anyone help and explain? Also, feel…
Mir
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