在javascript中,为什么要写“var querystringtohash=函数querystringtohash(query)…”?

声明函数意味着它是在分析脚本块时定义的,而将其分配给变量则是在运行时完成的:

x(); // this works as the function is defined before the script block is executed

function x() {}

但是:

x(); // doesn't work as x is not assigned yet

var x = function() {}

可以有条件地为变量分配函数。例子:

var getColor;
if (color == 'red') {
  getColor = function() { return "Red"; }
} else {
  getColor = function() { return "Blue"; }
}