In PHP I can do:
// $post = 10; $logic = >; $value = 100
$valid = eval("return ($post $logic $value) ? true : false;");
So the statement above would return false.
Can I do something similar in JavaScript? Thanks!
Darren.
4 Answers
If you want to avoid eval, and since there are only 8 comparison operators in JavaScript, is fairly simple to write a small function, without using eval at all:
function compare(post, operator, value) {
switch (operator) {
case '>': return post > value;
case '<': return post < value;
case '>=': return post >= value;
case '<=': return post <= value;
case '==': return post == value;
case '!=': return post != value;
case '===': return post === value;
case '!==': return post !== value;
}
}
//...
compare(5, '<', 10); // true
compare(100, '>', 10); // true
compare('foo', '!=', 'bar'); // true
compare('5', '===', 5); // false
answered Jan 11, 2010 at 15:23
Christian C. Salvadó
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2 Comments
scaryguy
I love the endlessness of possibilities with coding. Cool shortener.
Qamar Stationwala
lot of people here suggesting using eval. please for the love of GOD do not use eval. xD avoid it like the plague. this is probably the best answer here
yes, there's eval in javascript as well. for most uses it's not considered very good practice to use it, but i can't imagine it is in php either.
var post = 10, logic = '>', value = 100;
var valid = eval(post + logic + value);
1 Comment
Afshin Mehrabani
Note: It's not safe.
A little late, but you could've done the following:
var dynamicCompare = function(a, b, compare){
//do lots of common stuff
if (compare(a, b)){
//do your thing
} else {
//do your other thing
}
}
dynamicCompare(a, b, function(input1, input2){ return input1 < input2;}));
dynamicCompare(a, b, function(input1, input2){ return input1 > input2;}));
dynamicCompare(a, b, function(input1, input2){ return input1 === input2;}));
Comments
JavaScript have an eval function too: http://www.w3schools.com/jsref/jsref_eval.asp
eval("valid = ("+post+logic+value+");");
$post $logic $valuereturns a boolean, so there's no need for? true : false...