if (1){
    console.log('真值');//真值
}
else{
    console.log('假值');
}

if (0){
    console.log('真值');
}
else{
    console.log('假值');//假值
}

//空陣列
if ([]){
    console.log('真值');//真值
}
else{
    console.log('假值');
}
//空物件
if ({}){
    console.log('真值');//真值
}
else{
    console.log('假值');
}

//null
if (null){
    console.log('真值');
}
else{
    console.log('假值');//假值
}
//undefined
if (undefined){
    console.log('真值');
}
else{
    console.log('假值');//假值
}

參考文獻:
JavaScript-Equality-Table (opens new window)
JavaScript 核心篇 (opens new window)

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