5. 动态执行 JS

动态执行 JS

eval

特点：同步，当前作用域

var a = 1
function exec(code) {var a = 2eval(code)
}
exec('console.log("a",a)')
console.log('sync')

setTimeout

特点：异步，全局作用域

var a = 1
function exec(code) {var a = 2setTimeout(code, 0)
}exec('console.log("a",a)')
console.log('sync')

创建 script 元素

特点：同步，全局作用域

var a = 1
function exec(code) {var a = 2const script = document.createElement('script')script.innerHTML = codedocument.body.appendChild(script)
}exec('console.log("a",a)')
console.log('sync')

Function

特点：同步，全局作用域

var a = 1
function exec(code) {var a = 2const fn = new Function(code)fn()
}exec('console.log("a",a)')
console.log('sync')