"use strict"; var x = 17; with (obj) { x; } //会报obj未定义的错误

"use strict"; var x; delete x; //运行正常

function f(a){ "use strict"; a = 42; return a==arguments[0]; } f(5); //运行结果为true

function f(str){ "use strict"; return eval(str); } f(‘alert(1)’); //运行正常，弹窗1的对话框