Html 在这段代码中如何返回布尔类型? 函数clickCounter(){ if(类型(存储)!=“未定义”){ 如果(localStorage.clickcount){/
ECMASCript定义了将表达式转换为布尔值的规则: 9.2 ToBooleanHtml 在这段代码中如何返回布尔类型? 函数clickCounter(){ if(类型(存储)!=“未定义”){ 如果(localStorage.clickcount){/,html,Html,ECMASCript定义了将表达式转换为布尔值的规则: 9.2 ToBoolean 编号: 如果参数为+0、-0或NaN,则结果为false;否则结果为true 那么,该语句相当于: <!DOCTYPE html> <html> <head> <script> function clickCounter() { if(typeof(Storage) !== "undefined") { if (localStor
- 编号: 如果参数为+0、-0或NaN,则结果为false;否则结果为true
<!DOCTYPE html>
<html>
<head>
<script>
function clickCounter() {
if(typeof(Storage) !== "undefined") {
if (localStorage.clickcount) {// <----- here!
localStorage.clickcount = Number(localStorage.clickcount)+1;
} else {
localStorage.clickcount = 1;
}
document.getElementById("result").innerHTML = "You have clicked the button " + localStorage.clickcount + " time(s).";
} else {
document.getElementById("result").innerHTML = "Sorry, your browser does not support web storage...";
}
}
</script>
</head>
<body>
<p><button onclick="clickCounter()" type="button">Click me!</button></p>
<div id="result"></div>
<p>Click the button to see the counter increase.</p>
<p>Close the browser tab (or window), and try again, and the counter will continue to count (is not reset).</p>
</body>
</html>
ECMASCript定义将表达式转换为布尔值的规则: 9.2 ToBoolean
- 编号: 如果参数为+0、-0或NaN,则结果为false;否则结果为true
<!DOCTYPE html>
<html>
<head>
<script>
function clickCounter() {
if(typeof(Storage) !== "undefined") {
if (localStorage.clickcount) {// <----- here!
localStorage.clickcount = Number(localStorage.clickcount)+1;
} else {
localStorage.clickcount = 1;
}
document.getElementById("result").innerHTML = "You have clicked the button " + localStorage.clickcount + " time(s).";
} else {
document.getElementById("result").innerHTML = "Sorry, your browser does not support web storage...";
}
}
</script>
</head>
<body>
<p><button onclick="clickCounter()" type="button">Click me!</button></p>
<div id="result"></div>
<p>Click the button to see the counter increase.</p>
<p>Close the browser tab (or window), and try again, and the counter will continue to count (is not reset).</p>
</body>
</html>
在此上下文中,您经常会看到一个术语truthy。MDN将其描述如下: 在JavaScript中,truthy值是在布尔上下文中计算时被视为true的值 来源:
if语句需要一个布尔值。它检查实际输入的内容,并将其解释为true(truthy)或false(falsy)。在此上下文中,您经常看到的术语是truthy。MDN将其描述如下: 在JavaScript中,truthy值是在布尔上下文中计算时被视为true的值 来源:
if语句需要一个布尔值。它检查实际输入的内容,并将其解释为true(truthy)或false(falsy)。这些情况返回false: 布尔值为false
数字为0\n
字符串为“”
var未定义
var为空
否则->返回true这些情况返回false: 布尔值为false
数字为0\n
字符串为“”
var未定义
var为空 否则->返回true