illustrate
In JavaScript, there are certain values that are considered "false", such as false, 0, the empty string '', null, undefined, and NaN. Except for these "false" values, all other values (including non-empty strings, numbers, objects, etc.) are considered "true". Therefore, the if(field){} statement checks whether the value of field is true. If the value of field is true, the statement in the if code block is executed; if the value of field is false, the if code block is skipped.
Here are a few examples:
const field1 = '';
if (field1) {
console.log('field1 is truthy'); // 不会输出，因为空字符串是“假”值
} else {
console.log('field1 is falsy');
}
const field2 = 'Some value';
if (field2) {
console.log('field2 is truthy'); // 输出，非空字符串是“真”值
} else {
console.log('field2 is falsy');
}
const field3 = null;
if (field3) {
console.log('field3 is truthy');
} else {
console.log('field3 is falsy'); // 输出，null是“假”值
}
const field4 = 0;
if (field4) {
console.log('field4 is truthy');
} else {
console.log('field4 is falsy'); // 输出，0是“假”值
}