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JavaScript -- write a function that can solve a math expression (without eval)
(2 answers)
Closed 3 years ago.
I'm working on a problem generator that spits out phrases like "!(A && B) || (A || B)", but it does so in a string (I have a function that spits this out in string form). How would I convert this string expression into a same boolean expression in javascript? I've tried to use JSON.parse() but it keeps giving me an error.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval should be the function you're looking for, however read the note about the huge security risk!
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Why can't I access a property of an integer with a single dot?
(5 answers)
Closed 7 months ago.
1.toString() gives us Uncaught SyntaxError: Invalid or unexpected token.
One the other hand, (1).toString() returns '1'.
Considering that typeof 1 === typeof (1) (both are of type number), why is this the case?
In JS number literals might be both integers and floats, so probably after finding . after the number translator expects to parse a float, like 1.123.
This question already has answers here:
Variable position in comparision in PHP
(4 answers)
Why do some experienced programmers write comparisons with the value before the variable? [duplicate]
(12 answers)
PHP conditional assignment
(1 answer)
Closed 2 years ago.
In many place, I've seen that there is used the expression if (value === expression) rather than if (expression === value).
For example, In php we use-
if (false === strpos('abc', 'a'))
And also I see after minifying JavaScript, the minified file also generated like this.
So my question is, what is the benefit of value === expression over expression === value?
Note: This question may be redundant but I may not get the proper keywords for searching. If it is duplicated then I am ready to close the question.
I don't think there is a difference because the idea of equality operator is that to check if both sides are have the same value, in === also same type.
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What does a tilde do when it precedes an expression?
(5 answers)
Closed 3 years ago.
code snippet of unirest
As you can see above, arrayIndexOf refers to a function. When invoking the arrayIndexOf function,
is it necessary to put "~" before "arrayIndexOf"? I try to change "~arrayIndexOf(value, field)" to "arrayIndexOf(value, field)". And it works as the same? Is there anything I miss?
In JavaScript, the tilde ~ Bitwise NOT operator is commonly used right
before an indexOf() to do a boolean check (truthy/falsy) on a string.
On its own, indexOf() returns the index number of a String object
passed in. So if -1 is returned it will be turned into 0 which is
falsy.
Source: https://wsvincent.com/javascript-tilde/
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How to convert a String containing Scientific Notation to correct Javascript number format
(8 answers)
Closed 5 years ago.
I have a string in response "2.222222522879E12",
When I do
parseFloat("2.222222522879E12")
2222222522879
But the expected value should be 2.22,
Whats happening ?
And how can I fix it
You're going to get 2.222222522879* 10^12 with that expression as E means exponent, or to the power of
As per your edit asking how to fix:
use the Number.prototype.toPrecision() function. Here is the documentation
This question already has answers here:
Calling member function of number literal
(3 answers)
Closed 6 years ago.
toString() doesn't work on numeric literal like 5.toString(), but it works on string literal ("str".toString()) or after the numeric literal is assigned to var, like var a = 5;a.toString(). Wondering why it doesn't work for the first case?
You can do this if you wrap it in parenthesis.
(5).toString();
The first dot is the decimal mark. You need a second one to access the property:
5..toString();