javascript - 这个 Javascript 函数参数是做什么的？

Question

考虑以下代码(为了清晰起见缩短了):

Vertices.chamfer = function(vertices, radius, quality, qualityMin, qualityMax) {
    radius = radius || [8];

    if (!radius.length)
    radius = [radius];
};

我将第一部分读为(伪代码):

if (radius array passed to function) then
  radius = radius
else
  radius = [8] // new array, single element of value 8
end if

但我没有得到第二个表达式(if(!radius.length) radius = [radius] 部分)。

谁能给我解释一下吗？

Answer 1

    Vertices.chamfer = function(vertices, radius, quality, qualityMin, qualityMax) {
            // Set the radius to the value passed in. 
            // If the value passed in is undefined, set the radius to an
            // array containing 8 (the "default")
            radius = radius || [8];

            // If radius isn't an array (i.e. length is 0 which evaluates to false), 
            // make it an array.
            if (!radius.length)
            radius = [radius];
        };