如何在javascript if语句中定义变量

Question

var x; 

function apply() {
    if (x = 1) {
        alert("show");
        document.getElementById("nav").style.display = "inline";
        var x = 2;
    } else {
        alert("hide");
        document.getElementById("nav").style.display = "none";
        var x = 1;
    }
}

function hide() {
    document.getElementById("nav").style.display = "none";
    x = 1;
    alert(x)
}

我在这段代码上遇到了麻烦。 我使用功能hide onload并将功能apply链接到按钮单击。

Answer 1

正确用法：

var x; // we define the variable x global outside the functions

function apply() {
    if (x == 1) { // you need to check with ==, with = you are just setting its value
        alert("show")
        document.getElementById("nav").style.display = "inline";
        x = 2 // change the varibale to 2
    } else {
        alert("hide")
        document.getElementById("nav").style.display = "none";
        x = 1 // change it to 1
    }

}

function hide() {
    document.getElementById("nav").style.display = "none";
    x = 1;
    alert(x)
}

Answer 2

您不能同时从if和if内部定义。 您应该从if内部删除“ var”