js判断var为空

if (variable === undefined || variable === null) {
    console.log('变量为空');
} else {
    console.log('变量不为空');
}

if (variable == null) {
    console.log('变量为空');
} else {
    console.log('变量不为空');
}

if (typeof variable === 'string' && variable.trim() === '') {
    console.log('变量是空字符串');
} else {
    console.log('变量不是空字符串');
}

function isEmpty(variable) {
    if (variable === null || variable === undefined) return true;
    if (typeof variable === 'string' && variable.trim() === '') return true;
    if (Array.isArray(variable) && variable.length === 0) return true;
    if (typeof variable === 'object' && Object.keys(variable).length === 0) return true;
    return false;
}

// 使用示例
if (isEmpty(variable)) {
    console.log('变量为空');
} else {
    console.log('变量不为空');
}

let data = ""; // 可以尝试不同的赋值进行测试

if (isEmpty(data)) {
    console.log('data 为空');
} else {
    console.log('data 不为空');
}

function isEmpty(variable) {
    if (variable === null || variable === undefined) return true;
    if (typeof variable === 'string' && variable.trim() === '') return true;
    if (Array.isArray(variable) && variable.length === 0) return true;
    if (typeof variable === 'object' && Object.keys(variable).length === 0) return true;
    return false;
}