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ViewsWhat does `value >= value` do in JavaScript?
Below is one of conditional statements from the source code of d3.min.
What is this checking for?:
value >= value
Here is the entire source code:
export default function min(values, valueof) {
let min;
if (valueof === undefined) {
for (const value of values) {
if (value != null
&& (min > value || (min === undefined && value >= value))) {
min = value;
}
}
} else {
let index = -1;
for (let value of values) {
if ((value = valueof(value, ++index, values)) != null
&& (min > value || (min === undefined && value >= value))) {
min = value;
}
}
}
return min;
}
·
Santiago Gelvez
2 answers
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It could be a peculiar form of checking against NaN (EDIT: and undefined):
const foo = 0/0; // NaN
let bar;
console.log(foo >= foo);
console.log(bar >= bar);Although why would anyone write it like that, instead of using the It's shorter than, say isNaN method, I cannot tell.!isNaN(value) && value !== undefined, but I'm not sure the tradeoff in legibility is worth it.
·
Santiago Gelvez
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Here's the >= comparison table created with editing this JSFiddle.
You can see value >= value is true except when value = undefined or value = NaN:
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Santiago Gelvez
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