javascript - 测试函数时未定义

Question

所以我一直在研究制作星形图案的函数，但不知何故，当我“innerHTML”它时，我总是得到“未定义”。谁能帮我看看我做错了什么？

pOutput.innerHTML = square(3);
poutput.innerHTML = rectangle(2,3);

function square(x) {
var z;
for (var i = 1; i<=x; i++) {
    for ( var j = 1; j<=x; j++) {
        z += "*";
    }
    z += "<br>";
}  
return z
}

function rectangle(x, y) {
var z;
for (var i = 1; i<=x; i++) {
    for ( var j = 1; j<=y; j++) {
        z += "*";
    }
    z += "<br>";
}  
return z  
}

Answer 1

你应该做 var z = "" 否则值是undefined，看这个:

var z;

console.log(z)

完整示例:

console.log(square(3));
console.log(rectangle(2,3));

function square(x) {
var z = "";
for (var i = 1; i<=x; i++) {
    for ( var j = 1; j<=x; j++) {
        z += "*";
    }
    z += "<br>";
}  
return z
}

function rectangle(x, y) {
var z = "";
for (var i = 1; i<=x; i++) {
    for ( var j = 1; j<=y; j++) {
        z += "*";
    }
    z += "<br>";
}  
return z  
}