I want to check if a value is in an accepted range. If yes, to do something; otherwise, something else.
The range is 0.001-0.009. I know how to use multiple if to check this, but I want to know if there is any way to check it in a single if statement.
You're asking a question about numeric comparisons, so regular expressions really have nothing to do with the issue. You don't need "multiple if" statements to do it, either:
if (x >= 0.001 && x <= 0.009) {
// something
}
You could write yourself a "between()" function:
function between(x, min, max) {
return x >= min && x <= max;
}
// ...
if (between(x, 0.001, 0.009)) {
// something
}
Here is an option with only a single comparison.
// return true if in range, otherwise false
function inRange(x, min, max) {
return ((x-min)*(x-max) <= 0);
}
console.log(inRange(5, 1, 10)); // true
console.log(inRange(-5, 1, 10)); // false
console.log(inRange(20, 1, 10)); // false
&& isn't a free lunch. I submitted a totally different O(3) solution below with 3 comparisons in a continuous chain, sans the &&, after inverting one of the boolean questions being asked.If you must use a regexp (and really, you shouldn't!) this will work:
/^0\.00([1-8]\d*|90*)$/
should work, i.e.
^ nothing before,0.00 (nb: backslash escape for the . character)$: followed by nothing else
If you're already using lodash, you could use the inRange() function:
https://lodash.com/docs/4.17.15#inRange
_.inRange(3, 2, 4);
// => true
_.inRange(4, 8);
// => true
_.inRange(4, 2);
// => false
_.inRange(2, 2);
// => false
_.inRange(1.2, 2);
// => true
_.inRange(5.2, 4);
// => false
_.inRange(-3, -2, -6);
// => true
You must want to determine the lower and upper bound before writing the condition
function between(value,first,last) {
let lower = Math.min(first,last) , upper = Math.max(first,last);
return value >= lower && value <= upper ;
}
Here's a short ES6 function:
const inRange = (num, min, max) => num >= min && num <= max
I like Pointy's between function so I wrote a similar one that worked well for my scenario.
/**
* Checks if an integer is within ±x another integer.
* @param {int} op - The integer in question
* @param {int} target - The integer to compare to
* @param {int} range - the range ±
*/
function nearInt(op, target, range) {
return op < target + range && op > target - range;
}
so if you wanted to see if x was within ±10 of y:
var x = 100;
var y = 115;
nearInt(x,y,10) = false
I'm using it for detecting a long-press on mobile:
//make sure they haven't moved too much during long press.
if (!nearInt(Last.x,Start.x,5) || !nearInt(Last.y, Start.y,5)) clearTimeout(t);
If you want your code to pick a specific range of digits, be sure to use the && operator instead of the ||.
if (x >= 4 && x <= 9) {
// do something
} else {
// do something else
}
// be sure not to do this
if (x >= 4 || x <= 9) {
// do something
} else {
// do something else
}const inRange = (num, num1, num2) => Math.min(num1, num2) <= num && Math.max(num1, num2) >= num;
Could be like this if you want to make inRange inclusive and not depend on order of range numbers (num1, num2).
Skip all the multiplications, max()/min() function calls, or logical AND (&&), and just do
function in_range(_, __, ___) {
return ((_ = +_) < +__) < (_ <= +___)
}
in_range(n, 0.001, 0.009)
It works because the boolean outcome described by this triple compare chain is inquiring whether
n <= max is TRUE but also n < min is FALSE
Which is same as inquiring about being within the [min, max] range. The logical equivalent is not(not A) and B, which is just another way of saying A and B. The comparison operators are so low-cost whether a short-circuiting && saves time is questionable.
0.0010
0.0011
0.0012
0.0013
0.0014
0.0015
.
.
.
0.0087
0.0088
0.0089
0.0090
A similar function can also be created for string comparisons in the same manner by removing the forced numeric coercions :
function in_range_str(_, __, ___) {
return (_ < __) < (_ <= ___)
}
So instead of having to invoke regex or check its byte ordinal value, one can test whether a byte is a uppercase letter in ASCII by doing
in_range_str(chr1, "A", "Z")
