SOURCE

function say (value) {
    alert(value);
}
function execute (someFunction, value) {
    someFunction(value);
}
// execute(say, 'hi js.');

function execute (someFunction, value) {
    someFunction(value);
}
// execute(function(value){alert(value);}, 'hi js.');

function say (value) {
    alert(value);
}
say // 回调函数