多少个问号“?"和冒号“:"在一个语句中用javascript解释?(有条件的运算符) [英] How multiple question marks "?" and colons ":" in one statement are interpreted in javascript? (Conditional Operators)

问题描述

我知道条件语句的解释方式很简单，例如

I know that how simple conditional statements are interpreted, like

condition ? expr1 : expr2 

但是我想知道如何解释这样的陈述?

But I wanted to know how such a statement is interpreted?

function arc() {
    ...
    return da >= d3_svg_arcMax ? r0 ? "String1" : "String2" : r0 ? "String3" : "String4";
}

无需解释此长表达.我只需要知道在此示例中同时使用多个问号和冒号是什么意思.

No need to explain this long expression. I just need to know what it means when multiple question marks and colons are used together like in this example.

谢谢

推荐答案

JavaScript是右关联的，因此您可以从右到左解析"三元.

Javascript is right-associative, so you 'resolve' the ternaries from right to left.

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