TypeScript const 

const numLivesForCat = 9;
const kitty = {
    name: "Aurora",
    numLives: numLivesForCat,
}

// Error
kitty = {
    name: "Danielle",
    numLives: numLivesForCat
};

// all "okay"
kitty.name = "Rory";
kitty.name = "Kitty";
kitty.name = "Cat";
kitty.numLives--;

编译结果 

var numLivesForCat = 9;
var kitty = {
    name: "Aurora",
    numLives: numLivesForCat,
};
// Error
kitty = {
    name: "Danielle",
    numLives: numLivesForCat
};
// all "okay"
kitty.name = "Rory";
kitty.name = "Kitty";
kitty.name = "Cat";
kitty.numLives--;

编译错误消息

error TS2450: Left-hand side of assignment expression cannot be a constant.