什么是Swift的JavaScript等价物？操作者

Question

在swift中,x = y ?? z意味着x等于y,除非y为null/nil,在这种情况下,x等于z.什么是JavaScript等价物？

Answer 1

x = y || z; //x is y unless y is null, undefined, "", '', or 0.

如果0要从falsey值中排除,

x = ( ( y === 0 || y ) ? y : z ); //x is y unless y is null, undefined, "", '', or 0.

或者如果你想false从falsey值中排除那么,

x = ((y === 0 || y === false || y) ? y : z);

DEMO

var testCases = [
  [0, 2],
  [false, 2],
  [null, 2],
  [undefined, 2],
  ["", 2],
  ['', 2],
]

for (var counter = 0; counter < testCases.length - 1; counter++) {
  var y = testCases[counter][0],
    z = testCases[counter][1],
    x = ((y === 0 || y === false || y) ? y : z);
  console.log("when y = " + y + " \t and z = " + z + " \t then x is " + x);
}